Helioseismic Magnetic Imager and Why We Study Helioseismology

Junwei Zhao

W. W. Hansen Experimental Physics Laboratory,Stanford University, Stanford, CA94305-4085

Lecture Plans

Lecture 1 HMI and why we want to do helioseismology studies

Lecture 2 HMI routine helioseismology results that you can

download and Use

Lecture 3Some helioseismology studies that may interest you

A New Era Is Coming for Solar Physics Research!

Shock waves generated by the rocket carrying SDO

Waves Are Everywhere!

Earthquake: Seismic Waves

Courtesy: CalTech Seismology Laboratory

海啸 : Tsunami Waves Generated by Chilean 8.9 Magnitude Earthquake

Sunquake: Helioseismic Waves

Kosovichev & Zharkova, 1998, Nature

EIT Waves

Possible MHD Waves in Chromosphere

Okamoto et al. 2007, Science

Half of HMI is Helioseismic, and the other half is Magnetic.

Just like seismology which studies seismic waves to derive Earth’s interior structures,

helioseismology is a science to study solar interior properties by studying helioseismic

waves.

Why do we study helioseismology?

Sunspots on the Solar Surface

courtesy: SOHO/MDI

Why Do We Study Helioseismology?• Solar surface magnetic field

We wonder where these magnetic field come from and where they go. We also wonder why these sunspots remain there for some time, and why they decay away.

SOHO/EIT Observation

Sunspot Butterfly Diagram

Magnetic Field Butterfly Diagram

Why Do We Study Helioseismology?• Solar surface magnetic field

We wonder where these magnetic field come from and where they go. We also wonder why these sunspots remain there for some time, and why they decay away.

• Solar activity cycles

Why does the Sun have 11-year activity cycles? Why did the Sun experience a very low and a very long minimum from 2007 to 2009?

Violent Solar Eruptions

courtesy: EIT, LASCO

Auroras on Planets Caused by Solar Storms

Left: persistent Saturnian auroras around its south pole

Right: Auroras seen in high latitude areas on the Earth

Figures credit: APOD

Why Do We Study Helioseismlogy?• Solar surface magnetic field

We wonder where these magnetic field come from and where they go. We also wonder why these sunspots remain there for some time, and why they decay away.

• Solar activity cycles

Why does the Sun have a 11-year activity cycle? Why did the Sun experience a very low and a very long minimum in the past 2 years or so.

• Solar storms and bad space weather

Solar storms may cause great troubles to man-made satellites in space and even power grids on the Earth. We wonder if we can better forecast space weather by a better understanding of the solar interior.

The Sun Rotates

400 years ago, Galileo Galilei observed the Sun’s rotation by tracking sunspots on its surface. Only very recently, scientists began to reveal solar interior rotation speed and meridional flow fields by use of helioseismology.

(courtesy: Rice Galileo Project)

Why Do We Study Helioseismology?• Solar surface magnetic field

We wonder where these magnetic field come from and where they go. We also wonder why these sunspots remain there for some time, and why they decay away.

• Solar activity cycles

Why does the Sun have a 11-year activity cycle? Why did the Sun experience a very low and a very long minimum in the past 2 years or so.

• Space storms and bad space weather

Space storms may cause great trouble to man-made satellites in space and even power grids on the Earth. We wonder if we can better forecast space weather by a better understanding of solar interior.

• Solar interior rotational and meridional flowsPrecise determination of solar interior rotational and meridional flow fields are crucial to understand solar dynamo.

Undoubtedly, helioseismology is very important to understand our star, the Sun. That is why NASA spends hundreds of millions of dollars to sponsor HMI.

Shift with time due to Michelson drift. (black is April and red is July)

Daily variation in equatorial rotation speed.

Instrument Status - Milestones

• Launch: February 10, 15:23UT

• Power : February 14, 01:44

• Open door: March 24, 15:04UT

– First light

• Science data: March 24, 23:10UT

– About 94% coverage since then.

• Regular operations: April 30, 22:24UT

– More than 99.9% complete

– Regular observables>99% of time

HMI first light

Eclipse Interrupts Data

One Image of the Sun

Granulation on Solar Surface

Full-Disk Dopplergram

Full Coverage of Emerging Active Region

Performance – Power Spectrum

Courtesy Tom Duvall