The Helioseismic and Magnetic Imager (HMI) instrument and investigation as a part of the NASA Solar Dynamics Observatory (SDO) is designed to study convection-zone dynamics and the solar dynamo, the origin and evolution of sunspots, active regions, and complexes of activity, the sources and drivers of solar magnetic activity and disturbances, links between the internal processes and dynamics of the corona and heliosphere, and precursors of solar disturbances for space-weather forecasts. A brief overview of the instrument, investigation objectives, and standard data products is presented.

/pdf/the-helioseismic-and-magnetic-imager-hmi-investigation-for-2omq27f3k3.pdf

The Helioseismic and Magnetic Imager (HMI) Investigation for the Solar Dynamics Observatory (SDO)

Monthly Notices is one of the three largest general primary astronomical research publications. It is an international journal, published by the Royal Astronomical Society. This article 1 describes its publication policy and practice.

Monthly Notices of the Royal Astronomical Society

We propose a new model for the initiation of a solar coronal mass ejection (CME). The model agrees with two properties of CMEs and eruptive flares that have proved to be very difficult to explain with previous models: (1) very low-lying magnetic field lines, down to the photospheric neutral line, can open toward infinity during an eruption; and (2) the eruption is driven solely by magnetic free energy stored in a closed, sheared arcade. Consequently, the magnetic energy of the closed state is well above that of the posteruption open state. The key new feature of our model is that CMEs occur in multipolar topologies in which reconnection between a sheared arcade and neighboring flux systems triggers the eruption. In this "magnetic breakout" model, reconnection removes the unsheared field above the low-lying, sheared core flux near the neutral line, thereby allowing this core flux to burst open. We present numerical simulations that demonstrate our model can account for the energy requirements for CMEs. We discuss the implication of the model for CME/flare prediction.

https://iopscience.iop.org/article/10.1086/306563/pdf

A Model for Solar Coronal Mass Ejections

The ideal helical kink instability of a force-free coronal magnetic flux rope, anchored in the photosphere, is studied as a model for solar eruptions. Using the flux rope model of Titov and D?moulin as the initial condition in MHD simulations, both the development of helical shape and the rise profile of a confined (or failed) filament eruption (on 2002 May 27) are reproduced in very good agreement with the observations. By modifying the model such that the magnetic field decreases more rapidly with height above the flux rope, a full (or ejective) eruption of the rope is obtained in very good agreement with the developing helical shape and the exponential-to-linear rise profile of a fast coronal mass ejection (CME) on 2001 May 15. This confirms that the helical kink instability of a twisted magnetic flux rope can be the mechanism of the initiation and the initial driver of solar eruptions. The agreement of the simulations with properties that are characteristic of many eruptions suggests that they are often triggered by the kink instability. The decrease of the overlying field with height is a main factor in deciding whether the instability leads to a confined event or to a CME.

https://iopscience.iop.org/article/10.1086/462412/pdf

Confined and Ejective Eruptions of Kink-unstable Flux Ropes

Solar Probe Plus (SPP) will be the first spacecraft to fly into the low solar corona. SPP’s main science goal is to determine the structure and dynamics of the Sun’s coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what processes accelerate energetic particles. Understanding these fundamental phenomena has been a top-priority science goal for over five decades, dating back to the 1958 Simpson Committee Report. The scale and concept of such a mission has been revised at intervals since that time, yet the core has always been a close encounter with the Sun. The mission design and the technology and engineering developments enable SPP to meet its science objectives to: (1) Trace the flow of energy that heats and accelerates the solar corona and solar wind; (2) Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind; and (3) Explore mechanisms that accelerate and transport energetic particles. The SPP mission was confirmed in March 2014 and is under development as a part of NASA’s Living with a Star (LWS) Program. SPP is scheduled for launch in mid-2018, and will perform 24 orbits over a 7-year nominal mission duration. Seven Venus gravity assists gradually reduce SPP’s perihelion from 35 solar radii (
 $R_{S}$
 ) for the first orbit to ${<}10~R_{S}$
 for the final three orbits. In this paper we present the science, mission concept and the baseline vehicle for SPP, and examine how the mission will address the key science questions

/pdf/the-solar-probe-plus-mission-humanity-s-first-visit-to-our-e2fb5pur3z.pdf

The Solar Probe Plus Mission: Humanity’s First Visit to Our Star

We describe the latest applications of our global three-dimensional magnetohydrodynamic (MHD) model of the solar corona and the solar wind. The model uses boundary conditions based on observed photospheric magnetic fields. It has been used in the simplified, “polytropic” approximation of the energy equation to study the geometrical and topological properties of the magnetic field (e.g., the location and evolution of corona holes, the reproduction of streamer structure, the location of the heliospheric current sheet). However, this approximation does not reproduce the density and temperature contrasts between open and closed-field regions and does not address data from EUV and X-ray emission. Our improved MHD model that includes energy transport (radiative losses, anisotropic thermal conduction, and coronal heating) in the transition region and solar corona is capable of reproducing many emission properties as observed by SoHO and Hinode.

MHD Simulations of the Global Solar Corona and the Solar Wind

Kinetic stability of large-scale MHD modes☆

Understanding Eruptive Phenomena with Thermodynamic MHD Simulations

The solar magnetic field plays a key role in determining coronal The principal input to MHD models is the observed solar magnetic field 3D MHD models can be used to compare with eclipse and coronograph images, SOHO images (LOSCO, EIT), Ulysses and WIND spacecraft data, and interplanetary scintillation (IPS) measurements MHD computations can tell us about the structure of the corona Eclipses can help us to verify the accuracy of the models 4 December, 2002 total eclipce: visible in the southern hemisphere (South Atlantic, southern Africa, Indian Ocean, and Australia) Total in center Angola is at 06:00 UT

Zoran Mikic

Papers

MHD Simulations of the Global Solar Corona and the Solar Wind

Kinetic stability of large-scale MHD modes☆

Understanding Eruptive Phenomena with Thermodynamic MHD Simulations

Predicting the Structure of the Solar Corona During the December 4, 2002 Total Solar Eclipse

Where is the Open Flux