Report of Solar Geophysical Activity (RSGA)

Joint USAF/NOAA Solar Geophysical Activity Report and Forecast
SDF Number 269 Issued at 2200Z on 26 Sep 2013

IA.  Analysis of Solar Active Regions and Activity from 25/2100Z to
26/2100Z: Solar activity has been at very low levels for the past 24
hours. There are currently 4 numbered sunspot regions on the disk.
IB.  Solar Activity Forecast: Solar activity is expected to be very low
with a chance for a C-class flares on days one, two, and three (27 Sep,
28 Sep, 29 Sep).

IIA.  Geophysical Activity Summary 25/2100Z to 26/2100Z: The geomagnetic
field has been at quiet levels for the past 24 hours. Solar wind speed,
as measured by the ACE spacecraft, reached a peak speed of 402 km/s at
25/2208Z.
IIB.  Geophysical Activity Forecast: The geomagnetic field is expected
to be at quiet levels on days one and two (27 Sep, 28 Sep) and quiet to
unsettled levels on day three (29 Sep).

III.  Event probabilities 27 Sep-29 Sep
Class M    05/05/05
Class X    01/01/01
Proton     01/01/01
PCAF       green

IV.  Penticton 10.7 cm Flux
Observed           26 Sep 110
Predicted   27 Sep-29 Sep 110/110/110
90 Day Mean        26 Sep 111

V.  Geomagnetic A Indices
Observed Afr/Ap 25 Sep  004/005
Estimated Afr/Ap 26 Sep  002/003
Predicted Afr/Ap 27 Sep-29 Sep  004/005-005/005-007/008

VI.  Geomagnetic Activity Probabilities 27 Sep-29 Sep
A.  Middle Latitudes
Active                05/05/10
Minor Storm           01/01/01
Major-severe storm    01/01/01
B.  High Latitudes
Active                15/15/20
Minor Storm           15/15/20
Major-severe storm    05/05/10

Radio Events Observed 26 Sep 2013
A.  245 MHz Bursts
No 245 MHz Burst Observed.
B.  245 MHz Noise Storms
No 245 MHz Noise Storms Observed.

Solar Radio Data

Scientists monitor the structure of the solar corona, the outer most regions of the Sun's atmosphere, using radio waves -- the surface of the Sun is 6,000 degrees Kelvin, while the high corona can reach several million degrees Kelvin. Solar radio emissions at different frequencies allow us to observe radiation from different heights in the atmosphere. The lower the frequency, the higher the height of origin. The frequency, like the electron density, decreases uniformly outwards: 245 MHz originates high in the corona, while 15,400 MHz originates in the low corona. The 5 MHz emission corresponds to about 10 solar radii height. For a detailed review, see McLean and Labrum (1985)SOLAR RADIOPHYSICS.

Radio bursts are associated with solar flares. The delay at Earth of the different radio frequencies during burst events is due to the outward movement of the source. Bursts can have temperatures of 10xE12 degrees Kelvin. Large bursts last 10 to 20 minutes on average. Longer radio noise storms of persistent and variable high levels of radiation originate in sunspot groups, areas of large, intense magnetic fields. These storms are strongly circularly polarized due to the intense magnetic fields.