Connecting the corona to the solar wind

Dr Peter Young

NASA Goddard Space Flight Center, USA

peter.r.young@nasa.gov

Thanks to Catania University for travel support, and thanks to staff and students for kind hospitality this week!

mailto:peter.r.young@nasa.gov

The solar wind is measured directly by in situ instruments

• single point measurements

The solar corona is measured globally by remote sensing

• spatial resolutions of ~ 1000 km

Fundamental Goal

Where does the in situ plasma originate in the solar corona?

Parker Solar Probe (NASA) Launched: 2018 Goes to 0.05 AU

Solar Orbiter (ESA/NASA) Launch date: Feb 2020 Goes to 0.3 AU

Both spacecraft go much closer to the Sun than current spacecraft (SOHO, SDO, etc.) - should be much easier to make the corona-solar wind connection

Coronal mass ejections (CMEs)

Sources of the solar wind

EUV corona at solar minimum

Where is the slow solar wind coming from in this image?

SOHO/EIT 195 Å image (1997)

Superradial expansion of magnetic field

An empirical relation between solar wind speed and the expansion factor of the solar wind was found by Wang & Sheeley (1990, ApJ)

Slow solar wind comes from boundary of coronal hole

http://connect-tool.irap.omp.eu/ Developed for Solar Orbiter

Active Region Outflows

Baker et al. (2009, ApJ)

• All active regions show one or more outflow [blue-shifted emission] patches at their edges

• Do they connect to the solar wind?

Sakao et al. (2007, Science)

Source of slow solar wind? • Only 1 of 7 AR outflow patches had direct connection to solar wind [Edwards et al. (2016,

Sol. Phys.)]

• May require 2-step process [Culhane et al. (2014, Sol. Phys.)]

Supporting evidence

Brooks & Warren (2011, ApJ) found solar wind element abundances (ACE) was consistent with the active region

The SPICE instrument on Solar Orbiter will be critical for making remote sensing velocity and element abundance measurements through UV spectroscopy

The dynamic solar wind: “Sheeley blobs”

Ejection of discrete plasma structures from the tops of streamers, 2-3 R☉ above the solar surface

Sheeley et al. (1997, ApJ)

Y.-M. Wang et al. (1998, ApJ)

The dynamic solar wind: periodic density structures

White light imaging from STEREO mission [Viall & Vourlidas, 2015, ApJ]

The dynamic solar wind

Processed white light images from STEREO [C. DeForest]

Kepko et al. (2016, GRL)

Periodict density structures can impact the Earth’s magnetosphere

“Corona to solar wind” project at NASA-Goddard

1. Differentiate which types and size scales of heliospheric structures emanate from which type of coronal structure.

2. Characterize these structures in the corona by composition and plasma parameters.

3. Use theory and modeling to test the formation mechanisms creating these solar wind structures.

4. Determine the geoeffectiveness of these structures.

Team

Nicki Viall (PI)

Peter MacNeice

Nick Arge

Georgia De Nolfo

Aleida Higginson (APL)

Larry Kepko

Aaron Roberts

Peter Young

Students, postdocs

Emily Mason (CUA)

Samantha Wallace (UNM)

Naty Alzate

Simone Di Matteo (Aquila)

The next NASA SMEX satellite: PUNCH

• PUNCH (PI: C. DeForest, SWRI) was selected by NASA on 20 June • Four “micro-sats” to image region from 6 to 180 solar radii • Major advance for connecting corona to heliosphere