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Update
WARNING
Geomagnetic K-index of 4 expected
Issued: Jul 28, 2021 07:22 PM UTC
Geomagnetic K-index of 4 expected
Valid From: 2021 Jul 28 1922 UTC
Valid To: 2021 Jul 29 0300 UTC
Warning Condition: Onset

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

ALERT
Geomagnetic K-index of 4
Issued: Jul 28, 2021 02:19 AM UTC
Geomagnetic K-index of 4
Threshold Reached: 2021 Jul 28 0218 UTC
Synoptic Period: 0000-0300 UTC

Active Warning: Yes

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

WARNING
Geomagnetic K-index of 4 expected
Issued: Jul 28, 2021 01:18 AM UTC
Geomagnetic K-index of 4 expected
Valid From: 2021 Jul 28 0117 UTC
Valid To: 2021 Jul 28 0900 UTC
Warning Condition: Onset

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

ALERT
Type II Radio Emission
Issued: Jul 25, 2021 06:11 AM UTC
Type II Radio Emission
Begin Time: 2021 Jul 25 0452 UTC
Estimated Velocity: 263 km/s

Description: Type II emissions occur in association with eruptions on the sun and typically indicate a coronal mass ejection is associated with a flare event.

ALERT
Type II Radio Emission
Issued: Jul 24, 2021 02:19 AM UTC
Type II Radio Emission
Begin Time: 2021 Jul 24 0010 UTC
Estimated Velocity: 554 km/s

Comment: Velocity values provided by the U.S. Air Force.

Description: Type II emissions occur in association with eruptions on the sun and typically indicate a coronal mass ejection is associated with a flare event.

ALERT
Geomagnetic K-index of 4
Issued: Jul 22, 2021 09:01 AM UTC
Geomagnetic K-index of 4
Threshold Reached: 2021 Jul 22 0900 UTC
Synoptic Period: 0900-1200 UTC

Active Warning: Yes

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

WARNING
Geomagnetic K-index of 4 expected
Issued: Jul 22, 2021 08:52 AM UTC
Geomagnetic K-index of 4 expected
Valid From: 2021 Jul 22 0851 UTC
Valid To: 2021 Jul 22 1500 UTC
Warning Condition: Onset

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

WATCH
Geomagnetic Storm Category G1 Predicted
Issued: Jul 21, 2021 08:29 PM UTC
Geomagnetic Storm Category G1 Predicted

Highest Storm Level Predicted by Day:
Jul 22: None (Below G1) Jul 23: G1 (Minor) Jul 24: None (Below G1)

THIS SUPERSEDES ANY/ALL PRIOR WATCHES IN EFFECT

Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Spacecraft - Minor impact on satellite operations possible.
Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.

ALERT
Type II Radio Emission
Issued: Jul 17, 2021 06:08 AM UTC
Type II Radio Emission
Begin Time: 2021 Jul 17 0510 UTC
Estimated Velocity: 439 km/s

Description: Type II emissions occur in association with eruptions on the sun and typically indicate a coronal mass ejection is associated with a flare event.

ALERT
Geomagnetic K-index of 4
Issued: Jul 14, 2021 04:41 PM UTC
Geomagnetic K-index of 4
Threshold Reached: 2021 Jul 14 1631 UTC
Synoptic Period: 1500-1800 UTC

Active Warning: No

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

WARNING
Geomagnetic K-index of 4 expected
Issued: Jul 14, 2021 04:39 PM UTC
Geomagnetic K-index of 4 expected
Valid From: 2021 Jul 14 1639 UTC
Valid To: 2021 Jul 15 0300 UTC
Warning Condition: Onset

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

ALERT
Type II Radio Emission
Issued: Jul 9, 2021 12:03 PM UTC
Type II Radio Emission
Begin Time: 2021 Jul 09 1048 UTC
Estimated Velocity: 745 km/s

Description: Type II emissions occur in association with eruptions on the sun and typically indicate a coronal mass ejection is associated with a flare event.

ALERT
Type II Radio Emission
Issued: Jul 3, 2021 04:24 PM UTC
Type II Radio Emission
Begin Time: 2021 Jul 03 1437 UTC
Estimated Velocity: 357 km/s

Description: Type II emissions occur in association with eruptions on the sun and typically indicate a coronal mass ejection is associated with a flare event.

SUMMARY
X-ray Event exceeded X1
Issued: Jul 3, 2021 03:00 PM UTC
X-ray Event exceeded X1
Begin Time: 2021 Jul 03 1418 UTC
Maximum Time: 2021 Jul 03 1429 UTC
End Time: 2021 Jul 03 1434 UTC
X-ray Class: X1.5
Optical Class: sf
Location: N25W86
NOAA Scale: R3 - Strong

Potential Impacts: Area of impact consists of large portions of the sunlit side of Earth, strongest at the sub-solar point.
Radio - Wide area blackout of HF (high frequency) radio communication for about an hour.

ALERT
X-Ray Flux exceeded M5
Issued: Jul 3, 2021 02:34 PM UTC
X-Ray Flux exceeded M5
Threshold Reached: 2021 Jul 03 1427 UTC
NOAA Scale: R2 - Moderate

Potential Impacts: Area of impact centered on sub-solar point on the sunlit side of Earth. Extent of blackout of HF (high frequency) radio communication dependent upon current X-ray Flux intensity. For real-time information on affected area and expected duration please see http://www.swpc.noaa.gov/products/d-region-absorption-predictions-d-rap.

EXTENDED WARNING
Geomagnetic K-index of 4 expected
Issued: Jul 1, 2021 12:09 AM UTC
Geomagnetic K-index of 4 expected
Extension to Serial Number: 3915
Valid From: 2021 Jun 30 1726 UTC
Now Valid Until: 2021 Jul 01 0600 UTC
Warning Condition: Persistence

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

ALERT
Geomagnetic K-index of 4
Issued: Jun 30, 2021 09:01 PM UTC
Geomagnetic K-index of 4
Threshold Reached: 2021 Jun 30 2059 UTC
Synoptic Period: 1800-2100 UTC

Active Warning: Yes

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Aurora - Aurora may be visible at high latitudes such as Canada and Alaska.

Table

Date Radio flux 10.7 cm SESC Sunspot number Sunspot area 10E-6 New regions GOES15 X-ray Bkgd flux Flares
X-ray Optical
C M X S 1 2 3
Jun 30, 2021 94 53 540 0 * 2 0 0 3 0 0 0
Jul 01, 2021 94 56 810 0 * 0 0 0 1 0 0 0
Jul 02, 2021 95 72 600 0 * 0 0 0 0 0 0 0
Jul 03, 2021 94 81 680 1 * 3 2 1 11 0 0 0
Jul 04, 2021 91 60 590 1 * 4 1 0 8 0 0 0
Jul 05, 2021 89 43 530 0 * 2 0 0 2 0 0 0
Jul 06, 2021 83 52 330 1 * 2 0 0 0 0 0 0
Jul 07, 2021 76 25 20 0 * 0 0 0 0 0 0 0
Jul 08, 2021 73 23 20 0 * 0 0 0 0 0 0 0
Jul 09, 2021 74 23 30 1 * 3 0 0 0 0 0 0
Jul 10, 2021 74 24 80 1 * 0 0 0 0 0 0 0
Jul 11, 2021 74 23 70 0 * 0 0 0 1 0 0 0
Jul 12, 2021 72 22 70 0 * 0 0 0 0 0 0 0
Jul 13, 2021 72 11 50 0 * 0 0 0 0 0 0 0
Jul 14, 2021 72 23 70 1 * 0 0 0 0 0 0 0
Jul 15, 2021 74 22 30 0 * 0 0 0 0 0 0 0
Jul 16, 2021 75 35 70 1 * 2 0 0 2 0 0 0
Jul 17, 2021 77 53 90 1 * 0 0 0 1 0 0 0
Jul 18, 2021 80 42 80 0 * 0 0 0 1 0 0 0
Jul 19, 2021 83 45 130 1 * 1 0 0 1 0 0 0
Jul 20, 2021 87 59 250 1 * 1 0 0 0 0 0 0
Jul 21, 2021 94 86 260 2 * 2 0 0 2 0 0 0
Jul 22, 2021 89 77 290 0 * 0 0 0 0 0 0 0
Jul 23, 2021 87 46 80 0 * 1 0 0 2 0 0 0
Jul 24, 2021 84 35 40 0 * 1 0 0 0 0 0 0
Jul 25, 2021 82 24 30 0 * 0 0 0 0 0 0 0
Jul 26, 2021 81 25 20 0 * 0 0 0 0 0 0 0
Jul 27, 2021 80 25 0 0 * 0 0 0 1 0 0 0
Jul 28, 2021 79 0 0 0 * 0 0 0 2 0 0 0
Jul 29, 2021 76 0 0 0 * 0 0 0 0 0 0 0
Average/Total 82 39 195 12 24 3 1 38 0 0 0

Summary graph

Flares

Solar wind

Solar Wind

The solar wind is a stream of plasma released from the upper atmosphere of the Sun. It consists of mostly electrons, protons and alpha particles with energies usually between 1.5 and 10 keV. The stream of particles varies in density, temperature, and speed over time and over solar longitude. These particles can escape the Sun's gravity because of their high energy, from the high temperature of the corona and magnetic, electrical and electromagnetic phenomena in it.

The solar wind is divided into two components, respectively termed the slow solar wind and the fast solar wind. The slow solar wind has a velocity of about 400 km/s, a temperature of 1.4–1.6×10e6 K and a composition that is a close match to the corona. By contrast, the fast solar wind has a typical velocity of 750 km/s, a temperature of 8×10e5 K and it nearly matches the composition of the Sun's photosphere. The slow solar wind is twice as dense and more variable in intensity than the fast solar wind. The slow wind also has a more complex structure, with turbulent regions and large-scale structures.

Solar radio flux at 10.7 cm

Solar radio flux at 10.7 cm

The solar radio flux at 10.7 cm (2800 MHz) is an excellent indicator of solar activity. Often called the F10.7 index, it is one of the longest running records of solar activity. The F10.7 radio emissions originates high in the chromosphere and low in the corona of the solar atmosphere. The F10.7 correlates well with the sunspot number as well as a number of UltraViolet (UV) and visible solar irradiance records. Reported in “solar flux units”, (s.f.u.), the F10.7 can vary from below 50 s.f.u., to above 300 s.f.u., over the course of a solar cycle.

Flares

Flares

A solar flare is a sudden flash of brightness observed over the Sun's surface or the solar limb, which is interpreted as a large energy release of up to 6 × 10e25 joules of energy. They are often, but not always, followed by a colossal coronal mass ejection. The flare ejects clouds of electrons, ions, and atoms through the corona of the sun into space. These clouds typically reach Earth a day or two after the event.

Solar flares affect all layers of the solar atmosphere (photosphere, chromosphere, and corona), when the plasma medium is heated to tens of millions of kelvin, while the electrons, protons, and heavier ions are accelerated to near the speed of light. They produce radiation across the electromagnetic spectrum at all wavelengths, from radio waves to gamma rays, although most of the energy is spread over frequencies outside the visual range and for this reason the majority of the flares are not visible to the naked eye and must be observed with special instruments. Flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior. Flares are powered by the sudden (timescales of minutes to tens of minutes) release of magnetic energy stored in the corona. The same energy releases may produce coronal mass ejections (CME), although the relation between CMEs and flares is still not well established.

The frequency of occurrence of solar flares varies, from several per day when the Sun is particularly "active" to less than one every week when the Sun is "quiet", following the 11-year cycle (the solar cycle). Large flares are less frequent than smaller ones.

Classification

Solar flares are classified as A, B, C, M or X according to the peak flux (in watts per square metre, W/m2) of 100 to 800 picometre X-rays near Earth, as measured on the GOES spacecraft.

Classification Peak Flux Range at 100-800 picometer
W/m2
A < 10e-7
B 10e-7 to 10e-6
C 10e-6 to 10e-5
M 10e-5 to 10e-4
X 10e-4 to 10e-3
Z > 10e-3

An earlier flare classification is based on Hα spectral observations. The scheme uses both the intensity and emitting surface. The classification in intensity is qualitative, referring to the flares as: (f)aint, (n)ormal or (b)rilliant. The emitting surface is measured in terms of millionths of the hemisphere and is described below. (The total hemisphere area AH = 6.2 × 1012 km2.)

Classification Corrected area
(millionths of hemisphere)
S < 100
1 100 - 250
2 250 - 600
3 600 - 1200
4 > 1200

Sunspot number

Sunspots

Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They correspond to concentrations of magnetic field that inhibit convection and result in reduced surface temperature compared to the surrounding photosphere. Sunspots usually appear in pairs, with pair members of opposite magnetic polarity. The number of sunspots varies according to the approximately 11-year solar cycle.

Sunspot populations quickly rise and more slowly fall on an irregular cycle of 11 years, although significant variations in the number of sunspots attending the 11-year period are known over longer spans of time. For example, from 1900 to the 1960s, the solar maxima trend of sunspot count has been upward; from the 1960s to the present, it has diminished somewhat. Over the last decades the Sun has had a markedly high average level of sunspot activity; it was last similarly active over 8,000 years ago.

The number of sunspots correlates with the intensity of solar radiation over the period since 1979, when satellite measurements of absolute radiative flux became available. Since sunspots are darker than the surrounding photosphere it might be expected that more sunspots would lead to less solar radiation and a decreased solar constant. However, the surrounding margins of sunspots are brighter than the average, and so are hotter; overall, more sunspots increase the Sun's solar constant or brightness. The variation caused by the sunspot cycle to solar output is relatively small, on the order of 0.1% of the solar constant (a peak-to-trough range of 1.3 W/m2 compared to 1366 W/m2 for the average solar constant).

K-indices



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1 2 2 2 2 1



Data


Estimated Planetary

Estimated Planetary

Date A K-indices (UTC)
0h 3h 6h 9h 12h 15h 18h 21h
Jul 01, 2021 7 3 3 1 1 1 1 1 1
Jul 02, 2021 5 1 1 2 1 1 2 1 1
Jul 03, 2021 4 2 1 2 1 1 1 0 0
Jul 04, 2021 3 1 1 1 1 1 1 0 1
Jul 05, 2021 7 2 1 1 2 2 2 3 2
Jul 06, 2021 8 2 2 3 2 3 1 2 1
Jul 07, 2021 6 1 1 2 2 1 1 1 2
Jul 08, 2021 5 2 1 2 1 1 1 1 1
Jul 09, 2021 5 2 2 2 1 1 1 0 2
Jul 10, 2021 6 3 2 1 1 1 1 2 2
Jul 11, 2021 4 1 0 0 1 1 1 1 1
Jul 12, 2021 7 1 1 1 1 2 2 2 3
Jul 13, 2021 5 2 1 1 1 1 1 1 1
Jul 14, 2021 14 1 1 1 2 3 4 4 3
Jul 15, 2021 10 2 3 2 2 2 2 3 3
Jul 16, 2021 4 2 1 1 0 1 1 2 1
Jul 17, 2021 4 2 1 1 1 1 2 1 1
Jul 18, 2021 4 1 1 1 1 1 1 0 2
Jul 19, 2021 7 2 3 3 1 1 1 2 2
Jul 20, 2021 10 3 2 3 2 1 2 3 3
Jul 21, 2021 6 2 2 1 2 2 2 1 0
Jul 22, 2021 11 2 2 4 4 3 1 1 1
Jul 23, 2021 4 1 1 1 1 1 1 1 2
Jul 24, 2021 4 1 2 1 2 1 1 0 1
Jul 25, 2021 3 0 1 1 1 1 0 1 1
Jul 26, 2021 4 1 1 1 1 1 0 1 1
Jul 27, 2021 6 1 1 1 2 1 1 1 3
Jul 28, 2021 13 4 3 3 3 2 3 3 2
Jul 29, 2021 8 2 3 2 2 2 1 1 2
Jul 30, 2021 6 1 2 2 2 2 1

Middle Latitude

Date A K-indices
Jul 01, 2021 7 3 3 1 1 2 2 1 1
Jul 02, 2021 6 1 1 2 1 2 2 2 2
Jul 03, 2021 4 2 1 2 1 2 1 1 0
Jul 04, 2021 4 1 2 1 1 2 1 1 0
Jul 05, 2021 9 2 1 2 2 3 2 2 3
Jul 06, 2021 8 2 2 3 2 3 1 2 1
Jul 07, 2021 6 1 1 2 2 2 1 1 3
Jul 08, 2021 5 2 1 2 1 2 1 1 1
Jul 09, 2021 7 2 3 1 2 2 2 1 2
Jul 10, 2021 8 3 2 2 2 2 2 2 2
Jul 11, 2021 4 1 0 0 1 2 2 2 2
Jul 12, 2021 7 1 0 1 1 2 2 3 3
Jul 13, 2021 7 3 1 1 2 2 2 2 1
Jul 14, 2021 10 0 1 2 2 3 3 3 3
Jul 15, 2021 12 2 3 3 2 3 3 3 2
Jul 16, 2021 5 2 1 1 1 2 1 2 1
Jul 17, 2021 4 2 1 1 1 1 2 1 0
Jul 18, 2021 5 1 0 1 2 2 2 1 2
Jul 19, 2021 4 1 2 1
Jul 20, 2021 9 2 1 3 2 2 1 3 3
Jul 21, 2021 6 2 2 1 2 3 2 1 0
Jul 22, 2021 9 1 2 3 3 3 2 1 1
Jul 23, 2021 3 0 0 1 1 2 1 1 1
Jul 24, 2021 5 0 2 1 2 3 1 1 1
Jul 25, 2021 5 0 0 1 2 3 2 2 1
Jul 26, 2021 4 1 1 1 1 2 1 1 1
Jul 27, 2021 6 1 0 1 2 2 1 2 3
Jul 28, 2021 13 3 3 2 3 3 3 3 1
Jul 29, 2021 12 2 3 3 3 3 2 2 3
Jul 30, 2021 1 1 2 2 2 1

High Latitude

Date A K-indices
Jul 01, 2021 7 4 2 1 1 1 2 1 1
Jul 02, 2021 5 1 2 1 2 1 2 1 1
Jul 03, 2021 3 2 2 2 1 0 0 0 1
Jul 04, 2021 1 1 1 1 0 0 0 0 0
Jul 05, 2021 4 2 1 1 1 1 1 2 1
Jul 06, 2021 8 2 2 3 1 4 1 1 0
Jul 07, 2021 6 2 2 3 2 1 1 1 1
Jul 08, 2021 2 1 1 1 0 0 0 1 0
Jul 09, 2021 3 1 2 1 2 0 0 0 0
Jul 10, 2021 4 2 3 1 0 0 1 1 1
Jul 11, 2021 0 0 0 0 0 0 0 0 1
Jul 12, 2021 5 1 1 2 2 1 2 1 2
Jul 13, 2021 3 2 2 0 0 0 0 1 1
Jul 14, 2021 15 0 1 1 3 4 5 3 2
Jul 15, 2021 15 2 4 3 4 4 2 1 1
Jul 16, 2021 3 2 1 0 0 1 1 1 1
Jul 17, 2021 2 1 1 1 1 0 1 0 0
Jul 18, 2021 1 1 0 0 0 1 0 0 1
Jul 19, 2021 2 1 1 0
Jul 20, 2021 9 2 2 4 2 1 2 2 2
Jul 21, 2021 10 2 3 1 2 3 4 1 0
Jul 22, 2021 28 1 3 6 6 4 3 1 0
Jul 23, 2021 3 0 1 1 2 2 0 1 0
Jul 24, 2021 4 0 2 1 3 2 1 0 0
Jul 25, 2021 1 0 0 1 0 1 0 0 1
Jul 26, 2021 2 1 0 1 0 0 0 1 1
Jul 27, 2021 1 0 0 0 1 0 0 0 2
Jul 28, 2021 13 3 3 4 2 2 3 2 2
Jul 29, 2021 12 1 3 3 3 3 4 1 1
Jul 30, 2021 1 1 3 4 1 0

About

The K-index quantifies disturbances in the horizontal component of earth's magnetic field with an integer in the range 0–9 with 1 being calm and 5 or more indicating a geomagnetic storm. It is derived from the maximum fluctuations of horizontal components observed on a magnetometer during a three-hour interval. The label K comes from the German word Kennziffer meaning “characteristic digit”. The K-index was introduced by Julius Bartels in 1938.

The Estimated 3-hour Planetary Kp-index is derived at the NOAA Space Weather Prediction Center using data from the following ground-based magnetometers:

  • Sitka, Alaska
  • Meanook, Canada
  • Ottawa, Canada
  • Fredericksburg, Virginia
  • Hartland, UK
  • Wingst, Germany
  • Niemegk, Germany
  • Canberra, Australia

These data are made available thanks to the cooperative efforts between SWPC and data providers around the world, which currently includes the U.S. Geological Survey, Natural Resources Canada (NRCAN), the British Geological Survey, the German Research Centre for Geosciences (GFZ), and Geoscience Australia. Important magnetometer observations are also contributed by the Institut de Physique du Globe de Paris and the Korean Space Weather Center K-index Watches are issued when the highest predicted NOAA estimated Kp-indices for a day are K = 5, 6, 7, or >= 8 and is reported in terms of the NOAA G scale. K-index Warnings are issued when NOAA estimated Kp-indices of 4, 5, 6, and 7 or greater are expected. K-index Alerts are issued when the NOAA estimated Kp-indices reach 4, 5, 6, 7, 8, or 9.


More info
Data source: NOAA, Wikipedia

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