Science is a wonderful thing if one does not have to earn one’s living at it. -----Albert Einstein

Lecture 1: 日震学的意义及观测Lecture 2-3: time-distance 日震学Lecture 4: global日震学Lecture 5: ring-diagram日震学Lecture 6: 未来的日震学及展望

两节上机实习课

日震学在太阳物理中的意义及日震学的观测

赵俊伟斯坦福大学汉森试验物理实验室

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

Earthquake and SeismologyLeft: Earthquakes often cause damages. The main entrance to Stanford University collapsed due to 1906 San Francisco Earthquake.

Right: Earthquake can also do good to science. Seismology can help researchers to investigate the Earth’s interior.

Figures courtesy: Stanford Report, Nature

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

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

Hinode 观测到的一个黑子群

太阳活动区的浮现与消失

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

太阳风暴中的彗星

SOHO搭载的几架仪器观测到的太阳现象

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)

太阳的较差自转是太阳磁场形成的原因

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.

日震学的观测

我们能否观测恒星的内部 ?

At first sight it would seem that the deep interior of the Sun and stars is less accessible to scientific investigation than any other regions of the universe.

Our telescopes may probe farther and farther into the depths of space; but how can we ever obtain certain knowledge of that which is hidden behind substantial barriers?

What appliance can pierce through the outer layers of a star and test the conditions within? (written in 1926)

Sir Arthur Eddington(1882 – 1944)

可以用声音观测吗 ?

我们可以利用声音观测到肉眼所不能看到的东西 .

Investigate the Solar Interior by Analyzing Sound of the Sun

Various information regarding the solar interior structures and dynamics have been obtained from helioseismology analyses

日震学的观测 : 地面观测美国国立太阳天文台 Global Oscillation Network

Group (GONG)

Figure courtesy: GONG/NSO

日震学需要长达数小时甚至数天的连续观测。若做到这一点，一个办法就是夏季去南极观测，而早期的日震观测就是这样做的；另外一个办法就是环绕地球多处设置观测站。

日震学的观测 : 空间观测空间观测，既可以实现时间上的连续性，又可以做到 seeing-free. 但是问题是，如果出现故障，无法排除，而且造价通常较高。

日震学的观测 : 空间观测日本的 Hinode也进行日震学观测。但是由于其多普勒速度场的观测不能如预期实现，只能使用其 G-Band 和 CaH的观测，使得结果也不如预期。但是可以用于太阳极区的日震学研究，是其它观测所不能做到的。

右图显示了 Hinode跟 SOHO/MDI 的 k-图与 time-distance图的比较。

日震学的观测 : 空间观测AIA

HMI

EVE

太阳能板

SDO(Solar Dynamics Observatory)将如期在今年 12月份发射。 HMI(Helioseismic Magnetic Imager)将进行日震学与太阳横向和纵向场的观测。斯坦福大学成为 HMI 和 AIA的数据中心，每天接受大约2.0TB的数据。