The high energetic plasma and the embedded magnetic field of coronal mass ejections interact with planetary magnetospheres giving rise to transient perturbations such as geomagnetic storms. Predicting the geomagnetic impact of such interplanetary coronal mass ejections (ICME) is of utmost importance for the protection of our technological infrastructure that is affected by space weather. We use 3D compressible magnetohydrodynamic simulation of a star-planet system to model and study an ICME-Earth interaction event of 20th November 2003. In the modelled interaction, we observe a change in magnetopause shape and stand-off distance on ICME impact, day and night side reconnections and induction of high currents in the magnetosphere. We also notice the formation of a ring of strong equatorial current around the Earth, leading to a reduction of the geomagnetic field. We calculate the simulated reduction in the magnetic field and compare that to the observed geomagnetic indices in order to establish a predictive approach for geomagnetic storms. These simulations are expected to illuminate the physical processes that result in space weather impacts of stellar magnetic storms in planetary and exoplanetary systems.

Coronal mass ejections (CMEs), the large scale transient eruptions from the Sun, interact with the Earth’s magnetosphere while travelling into the heliosphere. The energetic interplanetary CME (ICME) at 1AU not only creates geomagnetic storms and disrupts the magnetic field structure around the Earth but also impacts the plasma environment, causes strong aurorae, and disturbs the radio and electrical transmission massively. We use 3D compressible magnetohydrodynamic simulation of a star-planet system and study the interesting magnetohydrodynamic processes like bow-shock, magnetopause, magnetotail, planet-bound current sheets, magnetic reconnections, atmospheric mass loss as well as particle injection, etc., when an ICME flux rope crosses the Earth at 1 AU. We use the uniformly twisted force-free flux rope model proposed by Gold and Hoyle in 1960 to initiate the ICME and vary the flux rope properties using actual observational data. We observe a change in magnetopause’s shape and the stand-off distance to the magnetopause. We notice twist helicity injection inside the magnetotail current system. We discover comparative increment in both the rates of atmospheric mass out-flow and solar wind in-flow in the vicinity of Earth during the geo-storm. Such studies will help us understand how energetic magnetic storms from a host star impact planetary magnetospheres and atmospheres with implications for planetary and exoplanetary habitability.

The solar polar fields play a crucial role in sustaining the solar dynamo mechanism. Observations and computational modelling indicates that the surface dynamics of active regions mediated via plasma flows, which leads to the polar field build-up, is a fundamental aspect of the solar dynamo mechanism; in fact, this surface mediated flux dynamics also known as the Babcock-Leighton mechanism, is now implicated to be the leading contributor to the Sun’s polar field, and thus also provides a window to the future solar cycle. This emergent understanding is one of the major drivers of novel mission concepts aiming to image the solar high latitudes from out of the ecliptic locations. Based on numerical simulations of the near-surface magnetic field dynamics and the Sun’s polar landscape, here we discuss what new insights may be provided by out-of-the ecliptic solar physics missions.

Coronal magnetic field evolution modulates our space environment via coronal mass ejections, flares, and changes in solar wind conditions. However, routine observations of magnetic field in the optically thin solar corona are not yet well-developed. Hence understanding the coronal magnetic field distribution using data-constrained global magnetohydrodynamic (MHD) models is of paramount importance nowadays. There are several factors which can drive the evolution e.g. flux emergence, photospheric flows, stratification in thermodynamic variables, solar wind conditions. Simulations using MHD models will help us generate the global magnetic field distribution, which can be constrained using total solar eclipse observations. Apart from this, such models have the potential to generate polarization characteristics utilizing the model output, which will help in better interpretation of data from future solar missions like PUNCH. We discuss the magnetic field distribution and polarization characteristics for past solar eclipses based on MHD simulations for global solar corona using a variety of approaches based on data-driven surface flux transport models, potential field source surface models and full MHD models.

Several studies suggest that magnetic reconnection plays an essential role to generate and accelerate most of the erupting coronal magnetic flux ropes such as coronal mass ejections (CMEs). We explore the connection between magnetic properties (magnetic flux and helicity) of interplanetary coronal mass ejection (ICME) flux-ropes (magnetic clouds [MCs]) and those of associated near-sun CME flux-ropes formed in situ by low corona magnetic reconnection. We identify the progenitor CMEs and their solar sources and derive the source region reconnection flux using the post-eruption arcade (PEA) method. Combining the reconnection flux and the geometrical properties of associated CMEs obtained by forward-modeling, we extract the magnetic properties of CME flux ropes at their source. To measure the magnetic properties of 1 AU ICME we use constant-α force-free cylindrical flux rope model fit to in situ observations and directly from the observed magnetic time series rotated to the cloud frame. We investigate whether a significant difference exists in magnetic properties of ICMEs if their solar source is composed of pre-existing flux-ropes (filaments). This study has significant implications in finding the role of reconnection in the formation of twisted flux ropes during a solar eruptive process that transport solar magnetic flux and helicity into interplanetary space.