Geomagnetic storming briefly reaches G2-Moderate levels

Geomagnetic storming briefly reaches G2-Moderate levels

During the last 24 hours, solar wind parameters reflected an enhanced solar wind environment due to the onset of a co-rotating interaction region (CIR) in advance of a negative polarity coronal hole high speed stream (CH HSS).  Solar wind speed increased from initial values near 350 km/s to around 600 km/s by 20:23 UTC on July 04. Wind speeds then decreased to about 500 km/s and maintained that speed by 12:30 UTC on July 5.

IMF total field strength (Bt) ranged from 2 nT to a peak of 23 nT around 19:00 UTC on July 4.  The Bz component generally varied between +10 nT to -13 nT through about 03:00 UTC on July 5, briefly reaching a maximum southward component of -22 nT at 19:11 UTC July 4. 

After 03:00 UTC on July 5, Bz didn't vary much beyond +/- 5 nT. The phi angle was in a predominately negative (towards) solar sector, consistent with the influence of the negative polarity CH HSS, SWPC said in their Forecast Discussion issued 12:30 UTC on July 5.

Solar wind parameters are expected to remain enhanced due to continued CH HSS influence on July 5 and through midday July 6 when CH HSS effects begin to wane.  CH HSS influence is expected to subside by late July 6/early July 7 with solar wind parameters expected to slowly return to background levels.

The geomagnetic field was at quiet to unsettled levels until 19:35 UTC on July 4 when G1 (Minor) geomagnetic storm conditions caused by the onset of a CIR/CH HSS were observed.  Field conditions increased to G2 (Moderate) levels at 02:47 UTC on July 5, but relaxed to G1 (minor) storm conditions by 06:00 UTC and further decreased to unsettled levels through period's end.

It is expected to be at unsettled to G1 (Minor) geomagnetic storm levels for the remainder of the UTC day  and unsettled to active levels on July 6 due to continued CH HSS effects.  A return to quiet to unsettled field activity is expected by July 7 as CH HSS influence subsides.


Space Weather Message Code: ALTK05
Serial Number: 798
Issue Time: 2015 Jul 04 1936 UTC

ALERT: Geomagnetic K-index of 5
Threshold Reached: 2015 Jul 04 1935 UTC
Synoptic Period: 1800-2100 UTC

Active Warning: Yes
NOAA Scale: G1 - Minor

NOAA Space Weather Scale descriptions can be found at

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.


Space Weather Message Code: ALTK06
Serial Number: 349
Issue Time: 2015 Jul 05 0248 UTC

ALERT: Geomagnetic K-index of 6
Threshold Reached: 2015 Jul 05 0247 UTC
Synoptic Period: 0000-0300 UTC

Active Warning: Yes
NOAA Scale: G2 - Moderate

NOAA Space Weather Scale descriptions can be found at

Potential Impacts: Area of impact primarily poleward of 55 degrees Geomagnetic Latitude.
Induced Currents - Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms.
Spacecraft - Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible.
Radio - HF (high frequency) radio propagation can fade at higher latitudes.
Aurora - Aurora may be seen as low as New York to Wisconsin to Washington state.


Featured image credit: NASA SDO AIA composite.

Register/become a supporter

Support us AD-FREE

Your support is crucial for our survival. It makes this project fully self-sustainable and keeps us independent and focused on the content we love to create and share. 

Monthly subscription

Subscription options

Yearly subscription

Subscription options

You'll receive your ad-free account for 20x faster browsing experience, clean interface without any distractions, ability to post comments without prior editorial check, all our desktop and mobile applications (current and upcoming) ad-free and with the full set of features available, a direct line of communication and much more. See all options.

Tags: g2 storm


No comments yet. Why don't you post the first comment?

Post a comment

Your name: *

Your email address: *

Comment text: *

The image that appears on your comment is your Gravatar