November 2007


Two sections from the Space Weather Predictions Center's "Weekly" 
publication - Preliminary Report of Solar and Geophysical Data that are
available in ascii text format and are described below.

Weekly publications are online at http://www.swpc.noaa.gov/weekly/
 
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HIGHLIGHTS AND FORECAST

The Weekly summarizes the solar activity, particle enhancements, 
and geomagnetic activity during the previous Monday through Sunday, and 
it provides a forecast of solar-geophysical conditions for the next 27 
days, beginning on Wednesday. In the activity summary and forecast, solar 
active regions are identified by the region number, heliographic latitude 
and longitude, and modified Zurich (McIntosh) sunspot classification/sunspot
area in millionths of the solar hemisphere on the date of maximum 
sunspot area;  for example, Region 4421 (N16, L=115, class/area, Dki/710 
on 27 February).  Significant solar activity is discussed in terms of the 
characteristics of the region of origin, x-ray flare class (C, M, or X), 
optical classification (SN, 1B, etc.), radio emission, energetic particle 
emission, and geophysical effects. The characteristics of near-Earth 
energetic proton events as detected by satellites and ground-based sensors 
are discussed. Geomagnetic storms and disturbances are described.  
Observations of visual aurora are included when available. Whenever 
feasible, solar and geomagnetic activity is summarized and forecast 
using standard terms.


Terms Used to Describe Solar Activity

   Very Low: x-ray events less than C-class.
   Low:  C-class x-ray events.
   Moderate: isolated (one to four) M-class x-ray events.
   High: several (5 or more) M-class x-ray events, or isolated 
         (one to four) M5 or greater x-ray events.
   Very High: several (5 or more) M5 or greater x-ray events. 



Terms Used to Describe Geomagnetic Activity


   The following adjectives are used to describe geomagnetic activity. 
   "A" refers to the 24 hour A index observed at a geomagnetic observatory 
   such as Fredericksburg, VA (middle latitude), and College, AK (high 
   latitude). "K" refers to a 3 hour index derived from the most disturbed 
   horizontal component of the local geomagnetic field. K is a quasi-
   logarithmic index ranging from 0 (very quiet) to 9 (highly disturbed). 


	Category	A index range		typical values  
	Quiet:           0 <= A <  8		usually no K indices > 2.
	Unsettled:       8 <= A < 16		usually no K indices > 3.
	Active:         16 <= A < 30		a few K indices of 4.
	Minor storm:    30 <= A < 50		K indices mostly 4 and 5.
	Major storm:    50 <= A <100		some K indices 6 or greater.
	Severe Storm:  100 <= A		        some K indices 7 or greater.


   Storms can begin either suddenly or gradually. If the beginning is 
   gradual, the reported begin time is the first hour when storm level 
   abrupt global changes in the magnetic field intensity, followed by storm-level 
   conditions occurred. Storm sudden commencements (SSCs) are distinctive, 
   abrupt global changes in the magnetic field intensity, followed by storm-level 
   conditions within approximately 24 hours.  Sudden Impulses (SIs) are also 
   abrupt global changes in the magnetic field, but subsequent activity does not  
   reach storm levels. The times of SIs and SSCs are given to the nearest 
   minute; for gradual commencements, to the nearest hour. An SI becomes an 
   SSC if it is followed by a geomagnetic storm.

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TWENTY-SEVEN DAY OUTLOOK

This section of the Weekly is a quantitative complement to the 27 
day forecast. Values are given for the next 27 days beginning 
on Wednesday.   Data are presented in tabular form. 
These 27 day forecasts are based primarily on the repetition of patterns 
of solar and/or geophysical activity with the period of the 27 day solar 
rotation (recurrence). Solar-terrestrial predictions on time scales of 27 
days to several years (medium term) are less developed than short-term 
(days) or solar cycle scale predictions. Recurrence of solar  
phenomena varies throughout the solar cycle, and therefore the accuracy 
of these forecasts is partly a function of the strength of recurrence. 
For example, geomagnetic activity resulting from stable coronal holes is most  
prevalent in the declining portion of the solar cycle, and the accuracy 
of 27 day geomagnetic forecasts based on recurrence is better during that 
time. The 10.7 cm flux forecast is likely to be less accurate during the 
rising phase of the cycle, when there are no long-lived active regions and 
active longitudes have yet to form. The outlook contains predicted 
planetary A index (Ap) and the largest expected Kp index; these values are 
intended for guidance only.  
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