Sun

The study of solar variability & heliospheric disturbances seeks to understand the Sun, determine how predictable solar activity truly is, and develop the capability to forecast solar activity and the evolution of solar disturbances as they propagate to Earth. It focuses on both short-term and long-term variability. X-ray flares can immediately and severely degrade radio communications through ionospheric effects.

Precursors to solar disturbances observable above and below the solar surface will initially serve as predictive tools for disruptive events. Coronal mass ejections that create large magnetic storms at Earth evolve significantly over their multi-day travel time to Earth. We will learn how disturbances initiate, propagate, and evolve from the Sun to Earth and incorporate this knowledge into a predictive model of geoeffectiveness at Earth to enable a warning and mitigation system for our technological assets.

Solar energetic particle events can pose serious threats to technological assets and astronauts in near-Earth orbit; we will learn how particles are accelerated in the inner heliosphere and how they propagate. We must also understand the long-term changes in total and spectral irradiance and the solar cycle variations that have signifi cant impacts on Earth's climate and human society.

Solar Flares
RHESSI data overlaid on a TRACE image shows gamma-rays (blue) and X-rays (red) thrown off by the hottest part of the 20 January 2005 flare. The gamma rays are made by energetic protons at the Sun.