instability - 2025 ACF Fall

Question

Astrophysical plasmas often experience a form of this phenomenon caused by the injection of a hot “stream” of particles. For 10 points each:

[10m] Name this phenomenon in which small perturbations cause a system to rapidly leave equilibrium, which shares its name with a property possessed by the inverted pendulum.

ANSWER: instability [or word forms like unstable; accept two-stream instability]

[10h] The two-stream instability is essentially the inverse of a damping process named for this Soviet physicist, who wrote a Course of Theoretical Physics with Evgeny Lifshitz and ranked the talent of physicists on a log-scale.

ANSWER: Lev Landau [or Lev Davidovich Landau]

[10e] Fluid instabilities occur when a wave’s frequency is one of these numbers, which equal a real number times the square root of negative one.

ANSWER: imaginary numbers [prompt on complex numbers]

<Editors, Physics>

Back to bonuses

Summary


Northern California	Main	Y	4	12.50	100%	0%	25%
Southern California	Main	Y	7	15.71	86%	29%	43%
Eastern Canada (1)	Main	Y	5	12.00	80%	20%	20%
Eastern Canada (2)	Main	Y	9	13.33	89%	33%	11%
Florida	Main	Y	4	10.00	100%	0%	0%
Great Lakes	Main	Y	12	11.67	100%	8%	8%
Lower Mid-Atlantic	Main	Y	9	10.00	100%	0%	0%
Upper Mid-Atlantic	Main	Y	2	10.00	100%	0%	0%
Midwest	Main	Y	9	13.33	100%	22%	11%
North	Main	Y	4	12.50	100%	25%	0%
Northeast	Main	Y	10	11.00	90%	10%	10%
Pacific	Main	Y	8	16.25	100%	38%	25%
South Central	Main	Y	6	8.33	67%	0%	17%
Southeast	Main	Y	13	10.00	77%	8%	15%
UK (North)	UK	Y	5	12.00	100%	0%	20%
UK (South)	UK	Y	7	14.29	100%	14%	29%
Upstate NY	Main	Y	5	12.00	100%	20%	0%

Data


Berkeley Archer Queen	Stanford B	0	0	10	10
Berkeley Mighty Miner	Berkeley Boss Bandit	0	10	10	20
Berkeley Little Prince	Stanford A	0	0	10	10
Claremont A	Claremont B	10	10	10	30
UCSD A	UC Santa Barbara	0	0	10	10
UCLA A	USC A	0	0	0	0
UCLA D	UCLA B	10	10	10	30
UCSD B	UCLA C	0	0	10	10
UCLA E	USC B	0	0	10	10
UC Irvine	UCLA F	0	10	10	20
Carleton A	Carleton B	0	0	10	10
McGill A	McGill B	0	10	10	20
Ottawa B	McGill C	0	0	0	0
McGill E	Ottawa C	10	0	10	20
Ottawa A	Ottawa D	0	0	10	10
Toronto E	McMaster B	0	10	10	20
McMaster C	Toronto I	10	0	10	20
Queen's A	Toronto F	0	0	10	10
Toronto A	Toronto C	10	0	10	20
McMaster A	Toronto B	0	0	10	10
Guelph A	Toronto G	0	0	10	10
Toronto H	Brock A	0	0	10	10
Toronto D	Waterloo A	0	0	0	0
Waterloo B	Waterloo C	10	0	10	20
Florida B	Florida A	0	0	10	10
Florida Tech B	ERAU Daytona A	0	0	10	10
South Florida A	Florida State A	0	0	10	10
Florida Tech A	UCF A	0	0	10	10
Michigan A	CWRU A	0	0	10	10
CWRU B	Louisville A	0	10	10	20
Ohio State B	CWRU D	0	0	10	10
Louisville D	Kentucky	0	0	10	10
Michigan B	Michigan State A	0	0	10	10
Louisville B	Michigan C	0	0	10	10
Ohio State A	Michigan State B	0	0	10	10
CWRU C	Ohio State C	0	0	10	10
Louisville C	Ohio State D	0	0	10	10
Michigan D	Pittsburgh	0	0	10	10
Michigan State C	WVU A	0	0	10	10
WVU B	Michigan State D	10	0	10	20
Duke A	Liberty A	0	0	10	10
JMU B	Liberty B	0	0	10	10
NCSU B	Liberty C	0	0	10	10
UNC A	NCSU A	0	0	10	10
Virginia Tech C	UNC C	0	0	10	10
UNC B	VCU A	0	0	10	10
William & Mary A	Virginia A	0	0	10	10
Virginia Tech A	Virginia Tech B	0	0	10	10
William & Mary B	William & Mary C	0	0	10	10
Maryland A	George Mason A	0	0	10	10
Rutgers A	Maryland C	0	0	10	10
Iowa A	Chicago A	0	0	10	10
Chicago B	Illinois Urbana	0	0	10	10
Illinois Blue	Illinois Champaign	10	0	10	20
Illinois Canada	Indiana A	10	0	10	20
Purdue A	Purdue C	0	0	10	10
Purdue B	Iowa B	0	10	10	20
William Woods University A	Rose-Hulman A	0	0	10	10
WashU Grizzlers	Indiana B	0	0	10	10
WashU Grolars	Purdue D	0	0	10	10
Iowa State	Macalester	10	0	10	20
Wisconsin B	Michigan Tech	0	0	10	10
St. Thomas	Wisconsin A	0	0	10	10
Wisconsin C	Minnesota	0	0	10	10
Amherst B	Tufts C	0	0	10	10
MIT A	Boston College A	10	10	10	30
Boston University A	Brandeis Bach	0	0	10	10
Amherst A	Brown A	0	0	10	10
Dartmouth B	Brown B	0	0	10	10
Dartmouth A	Vermont B	0	0	10	10
Harvard	Williams C	0	0	10	10
MIT B	Brandeis Beethoven	0	0	10	10
Tufts B	UConn A	0	0	0	0
Williams B	Brandeis Mozart	0	0	10	10
Alberta A	Washington Steelhead	10	0	10	20
Washington State	Arizona State A	0	0	10	10
Arizona State B	Washington Coho	10	10	10	30
Washington Masu	Boise State	0	0	10	10
Texas	British Columbia A	10	0	10	20
Washington Atlantic	British Columbia B	0	0	10	10
British Columbia C	Washington Chum	0	10	10	20
Washington Pink	Washington Sockeye	0	0	10	10
Central Oklahoma B	Kansas State A	0	0	0	0
Nebraska C	Murray State College B	0	0	10	10
Central Oklahoma A	Nebraska B	0	0	10	10
Murray State College A	Oklahoma	0	0	0	0
Tulsa A	Nebraska A	0	10	10	20
Harding	Tulsa B	0	0	10	10
Berkeley Skeleton King	UCSC	0	0	10	10
Auburn B	Auburn A	0	0	10	10
Auburn C	Mississippi State A	0	0	10	10
Durham A	Edinburgh A	0	0	10	10
Edinburgh C	Durham C	0	0	10	10
Durham D	Edinburgh B	0	10	10	20
Sheffield A	Durham B	0	0	10	10
York	Edinburgh D	0	0	10	10
Southampton	Birmingham	0	0	10	10
Cambridge D	Bristol	0	10	10	20
Imperial B	Cambridge C	0	0	10	10
Cardiff	Cambridge B	0	0	10	10
Warwick	Imperial A	0	0	10	10
Imperial D	Cambridge E	0	10	10	20
Oxford	Cambridge A	10	0	10	20
Binghamton C	Cornell B	0	0	10	10
ESF	Cornell A	0	0	10	10
RIT B	Cornell D	0	0	10	10
RIT A	Cornell C	0	0	10	10
Rochester	Binghamton B	10	0	10	20
Clemson B	Clemson C	0	0	10	10
Tennessee Tech	Georgia A	0	0	10	10
Georgia Tech F	Georgia Tech B	0	10	0	10
Georgia Tech C	Clemson A	0	0	10	10
Montevallo	Georgia Tech D	0	0	0	0
Georgia Tech E	Emory A	10	0	10	20
South Carolina A	Vanderbilt A	0	0	10	10
Georgia Tech A	Tennessee A	0	10	10	20
Tennessee B	Sewanne	0	0	10	10
Vanderbilt C	Vanderbilt B	0	0	10	10
Chipola College	Alabama A	0	0	0	0