Improvements of the shock arrival times at the Earth model STOA

Abstract:

Prediction of the shocks’ arrival times (SATs) at the Earth
is very important for space weather forecast. There is a well-known SAT model,
STOA, which is widely used in the space weather forecast. However, the shock
transit time from STOA model usually has a relative large error compared
to the real measurements. In addition, STOA tends to yield too much ‘yes’
prediction, which causes a large number of false alarms. Therefore, in this
work, we work on the modification of STOA model. First, we give a new method
to calculate the shock transit time by modifying the way to use the solar wind
speed in STOA model. Second, we develop new criteria for deciding whether
the shock will arrive at the Earth with the help of the sunspot numbers and
the angle distances of the flare events. It is shown that our work can improve
the SATs prediction significantly, especially the prediction of flare events with-
out shocks arriving at the Earth.