[Ips-wgr] ASWFC Weekly Geo. Report (18 December 25) issued 0051 UT on 18 Dec 2025 [SEC=OFFICIAL]

[Australian Space Weather Forecasting Centre]

SUBJ: ASWFC WEEKLY GEOPHYSICAL REPORT 
ISSUED ON 18 DECEMBER 2025
FROM THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE
ASWAS SCALE DESCRIPTION: https://bit.ly/3lmaMBx

1. SUMMARY (09 DECEMBER - 17 DECEMBER)
K indices are in UT (0-24). For conversion to local time:

AEST = UT + 10 hours; ACST = UT + 9.5 hours; AWST = UT + 8 hours
        Australian Region*              
 Date     K-INDICES    A               
 09 Dec   1011 1112    3  
 10 Dec   2231 2345   16  
 11 Dec   4322 2552   20  In the BOM magnetometer data for 11 
                          Dec, a weak (24nT) impulse was observed 
                          at 1500UT.
 12 Dec   3334 4355   26  
 13 Dec   3222 3322   10  
 14 Dec   1212 1121    4  
 15 Dec   1122 3111    5  
 16 Dec   3222 2322    9  
 17 Dec   3222 3233   11  

*estimated from real time data

NOTE: Indices may have been generated from data obtained in 
cooperation with the following organisations: Geoscience Australia, 
University of Newcastle Space Physics Group, Australian Government 
Antarctic Division and International Center for Space Weather 
Science and Education, Japan.


In the Australian region G1 periods were observed on 10-Dec, 11-Dec
and 12-Dec. Indistinct glancing CME arrivals were observed over 10-11 Dec
with a possible corotating interaction region on 12-Dec prior to the
Earth entering a coronal hole high speed wind stream. Planetary conditions
briefly reached G2 on 10-11 Dec and reached G1 on 12,13 and 18-Dec. 
G0 conditions were observed on other days of the week.

2. FORECAST (18 DECEMBER - 17 JANUARY)
Disturbed Periods: 
18 Dec,  21-24 Dec,  26-27 Dec,  30-31 Dec,  7-8 Jan.

Best Quiet Periods: 
 4-5 Jan,  10-11 Jan.

3. FORECAST FOR HIGH RESOLUTION AEROMAGNETIC SURVEYS
Northern Australian Regions:
 Mildly Disturbed Periods: 22-23 Dec.
 Best Quiet Periods: 18-20 Dec, 28-30 Dec, 03-11 Jan, 14-16 Jan.

Central Australian Regions:
 Disturbed Periods: 22-23 Dec
 Mildly Disturbed: 21-Dec, 24-27Dec, 31-Dec to 02-Jan, 09-10 Jan, 12-13 Jan.
 Best Quiet Periods: 19-Dec, 29-30 Dec, 04-07 Jan,  14-15 Jan.

Southern Australian Regions:
 Disturbed Periods: 21-27Dec, 31-Dec to 02-Jan, 09-10 Jan, 12-13 Jan.
 Best Quiet Periods: 19-Dec, 29-Dec, 04-07 Jan,  14-15 Jan.


Pc3 pulsations are high frequency (10-45 second period) variations 
of the Earths magnetic field. Daily pc3-indices are the daily sum of 
20 minute pc3-indices for that station and have been shown to be well 
correlated with rejection of high resolution aeromagnetic survey 
flight-line data.

PLEASE NOTE:
Geomagnetic activity can frequently be determined by short timescale 
solar events that cannot be forecast a week in advance, particularly
at solar maximum.

Australian Space Weather Forecasting Centre
Bureau of Meteorology
ASWFC at bom.gov.au
www.bom.gov.au | www.sws.bom.gov.au