Larry Klaes (firstname.lastname@example.org)
Fri, 30 Jul 1999 23:23:23 -0400
>From: "Cary Oler"<email@example.com>
>Subject: AstroAlert: Auroral Activity Watch for Middle Latitudes
>Date: Fri, 30 Jul 1999 21:01:39 -0600 (MDT)
>X-Mailer: ELM [version 2.4 PL24]
> | |
> Auroral Activity | A s t r o A l e r t | 31 July 1999
> WATCH | | 03:00 UTC
> ---------------- Sun-Earth Alert ----------------
> The arrival of a fairly vigorous solar disturbance at 19:48 UTC on
>30 July has resulted in considerable intensification of auroral activity,
>particularly during the last six hours.
> There is a fair to good possibility many middle latitude regions may
>spot periods of auroral activity over the next 12 to 18 hours. Recent data
>from the NOAA TIROS satellites suggests that moderate to strong auroral
>activity may be taking place at the present time. Unfortunately, there has
>not been any POLAR spacecraft imagery to compare with this since about 18:47
>UTC. The network of Canadian magnetometers indicates that periods of moderate
>auroral oval activity is indeed probably in progress.
> The near-full phase of the moon will hamper attempts to view activity,
>particularly for those where activity is typically close to the horizon. We
>don't expect this to become a severe auroral storm, but there is a good
>possibility that substorming over the higher latitudes could become intense
>enough to become visible from many middle latitude regions despite the full
>phase of the moon. Expansion of the auroral oval equatorward will also help
>bring periods of activity to the middle latitudes.
> For North American observers, the best chances of observing activity may
>be just prior to and shortly after moonrise. Statistically, the most intense
>phases of auroral activity occur during the hours around local midnight. This
>also corresponds to the most equatorward position of the auroral oval.
> At the present time, the main area of auroral activity should be
>spanning from western Europe to just off the U.S./Canada east coast.
>Over the next few hours, activity should become increasingly visible from
>North American middle and high latitude regions.
> Overall, we expect auroral activity to be frequently fairly quiescent
>with periods of moderate to strong bursts of substorm activity. During the
>quiescent periods, activity may appear as nothing more than a diffuse arc of
>light or a twilight-style glow to the north (or south if you're in Australia
>or New Zealand). During substorm periods, curtains, rays, pulsations of
>activity and color variations may be commonly observed. We do not expect
>auroral activity to become visible over widespread low latitude regions. For
>North America, most observations will probably be confined to the northern
>tier of the U.S. states and all of the Canadian provinces.
> The effects of this activity have already been manifested to those
>involved in ionospheric radio propagation. For a good example of the effects
>that can occur, tune your shortwave radio to radio stations WWV (Colorado) or
>WWVH (Hawaii) at 2.5, 5, 10, 15 or 20 MHz. During the evening hours, the
>ionosphere typically only supports propagation on the lower frequencies.
>Periods of stronger auroral activity are often audible in these signals as a
>rapid flutter (rapid fading that resembles a flutter). Similar signal
>effects may be observed with Radio Station CHU, in Ottawa (another time
>clock service) on frequencies 3.330, 7.335 and 14.670 MHz. There is a chance
>this activity may (at times) become intense enough to support VHF auroral
>backscattered signal propagation. For those without VHF radios, try tuning
>tuning your TV to the lower channels. For brief periods, it may be possible
>to pick up distant TV stations caused by their signals being reflected and
>refracted by the turbulent ionospheric conditions in and near the auroral
> We would appreciate receiving reports of observed odd radio signal
>propagation. Observers who witness activity may report their observations to
>us using the web page: http://solar.uleth.ca/www/subcaros.html. Within 5
>minutes, all reported observations are made available for others to read at
>the site: http://solar.uleht.ca/www/caros.html.
> If you spot auroral activity (regardless of your latitude), please make
>the observation available for others to see by posting to our main aurora
>submission site at: http://solar.uleth.ca/www/subaurora.html. All reported
>observations will be made available (within 5 minutes) on our auroral
>activity observers network page at: http://solar.uleth.ca/www/auroras.html.
>All observations are archived in our database of auroral activity sightings,
>which is made available to those performing research in this field.
> The locations of all ground-based reports that are submitted to us are
>also automatically plotted on our DMSP spacecraft-derived auroral oval map
>(as supplied from data from the USAF). This map, as well as near-realtime
>POLAR spacecraft imagery and derived statistical NOAA TIROS maps of
>near-realtime auroral oval activity (from SEC) can be found at:
>http://solar.uleth.ca/www/aurora.html. The University of Alberta,
>cooperating with the Canadian Space Agency and the CANOPUS project, also make
>available a near-realtime web resource that plots the estimated position of
>the auroral oval and associated activity based on the CANOPUS network of
>magnetometer data at: http://www.space.ualberta.ca/canopus.html.
> We appreciate those who participate in reporting auroral activity.
> This disturbance should begin subsiding later in the UTC day of
>31 July. Generally quiet conditions are expected to return on 01 August.
>** End of AstroAlert **
This archive was generated by hypermail 2.0b3 on Sun Aug 01 1999 - 16:28:48 PDT