Long-Term Solar Variability

Overview and Research Goal

The long-term variability of solar magnetism describes changes at the Sun that take place over the course of weeks, months, years, decades, and even centuries or longer. Such changes have profound consequences for the Earth's space environment, and, to a lesser extent, for its climate system. The origins and impacts of these changes have deep relevance to related variability in stars and stellar systems.

The research goal of LSV is to promote understanding of long-term solar variability from the Sun's interior out to the heliosphere. We will work with the community to achieve this using a combination of observations, theory, and numerical models to probe outstanding questions of magnetic dynamos, of convection and flows, of magnetic flux emergence and sunspots, of the evolution of the Sun's corona and the heliosphere, and of solar cycle variation.

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Research Highlights

Origins of the Ambient Solar Wind: Implication for Space Weather

Carrington rotation stack plots
Thursday, September 7, 2017

The Sun’s outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind.

MHD Simulations of the Eruption of Coronal Flux Ropes under Coronal Streamers

MHD simulations
Thursday, July 20, 2017

Using three-dimensional magnetohydrodynamic (MHD) simulations, we investigate the eruption of coronal flux ropes underlying coronal streamers and the development of a prominence eruption.

Solar Cycle Variability Induced by Title Angle Scatter in a Babcockl-Leighton Solar Dynamo Model

Variability in sunspot number (SSN) in STABLE dynamo simulations of the solar cycle using the observed random scatter in sunspot pair tilt angle of 15 degrees. (a) 19 magnetic cycles are highlighted with red and blue representing the northern and southern hemispheres respectively. Red shaded areas indicate periods when the SSN in the north exceeds that in the south and blue shaded areas indicate the opposite. (b) Long-term SSN variability in the same simulation, exhibiting extended periods of low and high a
Saturday, April 15, 2017

We present results from a three-dimensional Babcock–Leighton dynamo model that is sustained by the explicit emergence and dispersal of bipolar magnetic regions (BMRs). On average, each BMR has a systematic tilt given by Joy’s law.

A Theoretical Study of the Build-up of the Sun's Polar Magnetic Field by Using a 3D Kinematic Dynamo Model

Time evolution of two bipolar magnetic regions (BMRs)
Monday, January 9, 2017

We develop a three-dimensional kinematic self-sustaining model of the solar dynamo in which the poloidal field generation is from tilted bipolar sunspot pairs placed on the solar surface above regions of strong toroidal field by using the SpotMaker algorithm and then the transport of this poloida

Beyond sunspots: Studies using the McIntosh Archive of global solar magnetic

Thursday, December 15, 2016

In 1964 (Solar Cycle 20; SC 20), Patrick McIntosh began creating hand-drawn synoptic maps of solar magnetic features, based on H-alpha images.

AAS Nova Highlights Article About Measuring the Suns Activity On The Scale Used For The Stars

Cycle 23 data and cycle shape model fits
Wednesday, November 30, 2016

The American Astronomical Society (AAS) NOVA website is highlighting a recent publication by HAO's Ricky Egeland (graduate research fellow) titled The Mount Wilson Observatory S-Index of the Sun. The new paper has been accepted for publication in the Astrophysical Journal.

On the Fine Structure Splitting of the 3p43d4D5/2 and 3p43d4D7/2 Levels of FE X

Raw S082B image with wavelength scale
Thursday, October 20, 2016

We study UV spectra obtained with the SO82-B slit spectrograph on board SKYLAB to estimate the fine structure splitting of the Cl-like 3p43d4D5/2 and 3p43d4D7/2 levels of Fe X.

Babcock-Leighton Solar Dynamo: The Role of Downward Pumping and the Equatorward Propagation of Activity

Snapshots of poloidal field
Monday, October 10, 2016

The key elements of the Babcock-Leighton dynamos are the generation of poloidal field through decay and dispersal of tilted bipolar active regions and the generation of toroidal field through the observed differential rotation.

Convection in Oblate Solar-Type Stars

3D simulation image
Wednesday, July 13, 2016

We present the first global 3D simulations of thermal convection in the oblate envelopes of rapidly-rotating solar-type stars.

Improving Solar Dynamo Modeling

Kalman filtering image
Wednesday, February 11, 2015

Approximating a model’s “true” state by applying Kalman filtering to solar cycles, a technique first developed in the 1950s and 1960s to help Apollo 11 settle safely on the Moon.