Solar Physics, Heliophysics & Space Weather

Ofer CohenResearch Solar Physics, Heliophysics & Space Weather
The solar atmosphere and the interplanetary space are composed of ionized gas or “plasma”. The dynamic of this ionized material is governed by its interaction with magnetic fields. Understanding this interaction is important if we want to understand and predict changes on the Sun, the solar atmosphere, and the interplanetary space, and how these changes affect our planet and other planets. All the changes from the solar surface and above are driven by changes in the solar magnetic field. We can divide these changes into three time-scales:
1. In the short time-scales (hours to days), we have transient events in the solar corona that are known by the name Coronal Mass Ejections, or CMEs. CMEs are explosive events at which large amount of ionized gas is sent to space and perturb the ambient state of the interplanetary space. When CMEs reach Earth, they interact with its magnetic field and can drive geomagnetic storms that can impact satellite communication, polar commercial flights, and ground-based conducting systems due to a significant increase in radiation. The main science questions are how do CMEs are initiated, evolve, and propagate through space, and what is the detailed interaction between CMEs and the magnetic field of the Earth.

2. In the mid time-scale (months, one solar rotation of 27 days) we consider the ambient state of the solar corona and the interplanetary space. These changes are driven by changes in the solar magnetic field over these time scales. The main science questions are how does the solar corona get heated and how does the solar wind get accelerated. 

3. In the long time-scales (years to solar evolution time of billions of years) we consider the solar cycle at which the solar magnetic field reverses its polarity every 11 years, and the evolution of the Sun as a star. The main science questions are how does the solar magnetic field evolves with time and why does it flip, as well as how does the solar activity change with time.