SOHO/LASCO CME Catalog

CME heights (with respect to the disk center) are measured at the fastest segment of the leading edge.

PA= Position Angle measured from Solar North in degrees (counter-clockwise)

Halo CMEs are indicated in the "Central PA" column. The letters ("S", "BA", "OA") in the brackets show type of halo CMEs. See examples.

Click on date to view Java script movie of the CME.

Click on time to see height-time measurements as a text file.

Click on speed to view height-time plots of the CME.

Beware of data gaps. Check for LASCO/C2 data gaps here.

A complete description of the catalog

Click here to search the entire catalog.

First C2 Appearance
Date Time [UT] Central
PA
[deg] Angular
Width [deg] Linear
Speed [km/s] 2nd-order Speed at final height [km/s] 2nd-order Speed at 20 Rs [km/s] Accel
[m/s²] Mass
[gram] Kinetic
Energy
[erg] MPA [deg] Movies, plots, & links Remarks

2017/10/01 08:24:05 106 14 203 241 319 3.6^*1 ---- ---- 103 C2 C3 PHTX DST Java Movie Very Poor Event

2017/10/01 12:00:05 308 38 203 287 582 13.6^*1 1.7e+14 3.4e+28 300 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/01 13:25:43 44 14 272 276 311 1.1^*1 ---- ---- 53 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/01 22:24:05 261 59 171 272 493 10.0^*1 5.7e+14 8.4e+28 257 C2 C3 PHTX DST Java Movie Poor Event

2017/10/02 05:48:03 260 100 270 607 535 12.5^*1 6.1e+15 2.2e+30 262 C2 C3 PHTX DST Java Movie

2017/10/02 13:25:43 57 21 484 809 1428 88.2^*1 1.2e+14 1.4e+29 62 C2 C3 PHTX DST Java Movie Poor Event

2017/10/03 01:36:14 256 16 380 473 827 26.9^*1 ---- ---- 253 C2 C3 PHTX DST Java Movie Poor Event

2017/10/03 07:48:07 241 35 312 294 272 -1.5^*1 1.4e+14 6.6e+28 251 C2 C3 PHTX DST Java Movie Poor Event

2017/10/04 17:00:05 352 6 312 272 0 -26.4^*1 ---- ---- 351 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/05 04:00:05 49 17 253 226 0 -7.9^*1 ---- ---- 52 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/05 05:36:05 289 39 188 255 691 19.2^*1 1.0e+14 1.8e+28 288 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/05 10:48:05 259 8 392 467 519 7.6^*1 ---- ---- 259 C2 C3 PHTX DST Java Movie Poor Event

2017/10/05 14:12:05 289 62 261 380 849 29.7^*1 3.1e+14 1.1e+29 280 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/05 16:12:05 115 19 232 125 0 -14.7^*1 ---- ---- 107 C2 C3 PHTX DST Java Movie Very Poor Event

2017/10/05 20:36:05 270 53 201 122 0 -16.7^*1 2.4e+14 4.9e+28 277 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/05 22:36:07 252 44 206 470 449 8.7 2.9e+15 6.2e+29 253 C2 C3 PHTX DST Java Movie

2017/10/05 23:48:06 292 54 245 322 642 16.0^*1 1.5e+14 4.6e+28 275 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/06 08:12:05 53 10 223 131 0 -35.2^*1 ---- ---- 59 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/06 08:48:24 269 95 320 444 397 4.9 1.2e+16 6.0e+30 264 C2 C3 PHTX DST Java Movie

2017/10/07 01:36:11 290 48 259 278 418 4.9^*1 7.4e+13 2.5e+28 287 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/07 08:24:06 281 85 338 465 494 8.3 4.7e+15 2.7e+30 279 C2 C3 PHTX DST Java Movie

2017/10/08 03:12:10 302 12 276 329 327 2.4^*1 ---- ---- 298 C2 C3 PHTX DST Java Movie

2017/10/08 08:48:07 283 15 644 577 449 -13.5^*1 ---- ---- 276 C2 C3 PHTX DST Java Movie

2017/10/09 04:12:05 308 15 230 222 99 -1.9^*1 ---- ---- 301 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/09 05:36:05 271 104 327 442 416 5.3 9.6e+15 5.1e+30 264 C2 C3 PHTX DST Java Movie

2017/10/09 14:12:05 263 60 427 436 436 0.6 6.2e+14 5.7e+29 263 C2 C3 PHTX DST Java Movie

2017/10/10 03:24:05 260 16 375 470 660 15.3^*1 ---- ---- 265 C2 C3 PHTX DST Java Movie

2017/10/10 22:36:06 298 59 450 368 173 -10.6 7.5e+14 7.6e+29 302 C2 C3 PHTX DST Java Movie

2017/10/11 06:24:05 305 51 268 319 538 9.9 3.9e+14 1.4e+29 307 C2 C3 PHTX DST Java Movie Only C2

2017/10/11 15:12:09 285 109 741 611 585 -18.0 2.7e+15 7.5e+30 299 C2 C3 PHTX DST Java Movie

2017/10/11 20:57:24 55 15 217 251 645 15.8^*1 ---- ---- 61 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/11 23:24:05 297 50 487 538 828 21.0 1.6e+14 1.9e+29 305 C2 C3 PHTX DST Java Movie Only C2

2017/10/12 01:36:07 314 14 400 354 0 -13.6^*1 ---- ---- 311 C2 C3 PHTX DST Java Movie Only C2

2017/10/12 03:48:05 295 47 439 428 354 -3.2^*1 2.5e+13 2.4e+28 314 C2 C3 PHTX DST Java Movie Only C2

2017/10/12 09:12:08 320 17 370 449 779 22.0^*1 ---- ---- 313 C2 C3 PHTX DST Java Movie Only C2

2017/10/12 19:48:05 299 22 504 677 1546 96.4^*1 6.5e+13 8.3e+28 289 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/12 23:12:12 301 18 317 199 0 -23.4^*1 ---- ---- 309 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/13 02:48:05 316 60 315 388 851 27.9^*1 6.1e+13 3.0e+28 311 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/13 08:48:23 319 88 350 354 395 1.5^*1 2.6e+14 1.6e+29 296 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/13 21:12:10 61 13 375 325 0 -21.3^*1 ---- ---- 68 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/14 08:48:05 307 67 413 415 434 0.8^*1 3.5e+14 3.0e+29 312 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/14 16:00:05 66 37 307 308 310 0.1^*1 3.3e+14 1.5e+29 71 C2 C3 PHTX DST Java Movie

2017/10/15 10:48:05 67 16 359 455 1059 43.2^*1 ---- ---- 71 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/16 11:20:14 96 38 171 183 276 2.1^*1 4.2e+14 6.1e+28 101 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/16 13:46:33 86 62 213 166 0 -6.5^*1 2.7e+14 6.1e+28 102 C2 C3 PHTX DST Java Movie

2017/10/16 18:01:29 94 55 254 229 118 -2.7 8.4e+14 2.7e+29 104 C2 C3 PHTX DST Java Movie

2017/10/16 18:32:49 302 17 656 906 1731 117.2^*1 ---- ---- 299 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/16 21:30:36 94 64 266 227 164 -2.6 8.3e+14 2.9e+29 100 C2 C3 PHTX DST Java Movie

2017/10/17 03:15:31 94 70 440 473 476 2.6 4.6e+15 4.5e+30 100 C2 C3 PHTX DST Java Movie

2017/10/17 13:22:31 86 93 362 235 0 -11.3^*1 2.7e+15 1.8e+30 110 C2 C3 PHTX DST Java Movie

2017/10/18 05:48:05 Halo 360 1576 1355 1484 -44.5 5.7e+15^*2 7.0e+31^*2 137 C2 C3 PHTX DST Java Movie

2017/10/18 08:00:05 85 146 1001 665 928 -44.3 1.1e+16^*2 5.4e+31^*2 102 C2 C3 PHTX DST Java Movie Partial Halo

2017/10/19 14:48:06 20 91 285 376 770 23.3^*1 5.6e+14 2.3e+29 25 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/20 00:36:05 93 12 382 416 504 6.6^*1 ---- ---- 90 C2 C3 PHTX DST Java Movie Very Poor Event

2017/10/20 14:50:30 111 15 254 392 1163 55.6^*1 ---- ---- 110 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/21 00:00:05 98 109 331 259 306 -2.8 8.6e+15 4.7e+30 109 C2 C3 PHTX DST Java Movie

2017/10/21 14:36:05 5 4 487 586 1347 68.0^*1 ---- ---- 7 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/22 00:24:05 62 18 329 382 427 5.0^*1 ---- ---- 67 C2 C3 PHTX DST Java Movie Poor Event

2017/10/22 00:48:05 322 21 457 1050 3048 388.7^*1 1.0e+12^*2 1.1e+27^*2 321 C2 C3 PHTX DST Java Movie Very Poor Event; Only 3 points; Only C2

2017/10/22 21:48:05 352 7 400 429 893 27.3^*1 ---- ---- 354 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/25 03:36:05 287 11 165 145 0 -6.9^*1 ---- ---- 284 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/26 00:12:05 76 48 161 145 0 -6.2^*1 8.7e+13 1.1e+28 77 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/26 15:12:10 248 14 148 238 623 15.8^*1 ---- ---- 246 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/27 11:25:20 98 20 186 109 0 -41.7^*1 2.2e+13 3.8e+27 97 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/28 12:48:51 14 7 362 798 2639 289.4^*1 ---- ---- 18 C2 C3 PHTX DST Java Movie Very Poor Event; Only 3 points; Only C2

2017/10/28 18:00:05 296 10 412 622 1537 95.8^*1 ---- ---- 290 C2 C3 PHTX DST Java Movie Poor Event; Only C2

2017/10/29 17:25:20 255 24 312 345 371 2.6^*1 1.5e+15 7.4e+29 250 C2 C3 PHTX DST Java Movie Poor Event

2017/10/29 21:25:18 267 16 159 224 269 2.9^*1 ---- ---- 269 C2 C3 PHTX DST Java Movie Poor Event

2017/10/30 17:00:05 256 23 296 204 0 -27.4^*1 4.6e+13 2.0e+28 258 C2 C3 PHTX DST Java Movie Poor Event

2017/10/31 06:36:05 253 8 252 291 601 14.0^*1 ---- ---- 254 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

2017/10/31 11:48:05 32 8 313 314 326 0.3^*1 ---- ---- 35 C2 C3 PHTX DST Java Movie Very Poor Event; Only C2

First C2 Appearance Date Time [UT]	Central PA [deg]	Angular Width [deg]	Linear Speed [km/s]	2nd-order Speed at final height [km/s]	2nd-order Speed at 20 Rs [km/s]	Accel [m/s²]	Mass [gram]	Kinetic Energy [erg]	MPA [deg]	Movies, plots, & links	Remarks
2017/10/01	08:24:05	106	14	203	241	319	3.6^*1	----	----	103	C2 C3 PHTX DST Java Movie	Very Poor Event
2017/10/01	12:00:05	308	38	203	287	582	13.6^*1	1.7e+14	3.4e+28	300	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/01	13:25:43	44	14	272	276	311	1.1^*1	----	----	53	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/01	22:24:05	261	59	171	272	493	10.0^*1	5.7e+14	8.4e+28	257	C2 C3 PHTX DST Java Movie	Poor Event
2017/10/02	05:48:03	260	100	270	607	535	12.5^*1	6.1e+15	2.2e+30	262	C2 C3 PHTX DST Java Movie
2017/10/02	13:25:43	57	21	484	809	1428	88.2^*1	1.2e+14	1.4e+29	62	C2 C3 PHTX DST Java Movie	Poor Event
2017/10/03	01:36:14	256	16	380	473	827	26.9^*1	----	----	253	C2 C3 PHTX DST Java Movie	Poor Event
2017/10/03	07:48:07	241	35	312	294	272	-1.5^*1	1.4e+14	6.6e+28	251	C2 C3 PHTX DST Java Movie	Poor Event
2017/10/04	17:00:05	352	6	312	272	0	-26.4^*1	----	----	351	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/05	04:00:05	49	17	253	226	0	-7.9^*1	----	----	52	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/05	05:36:05	289	39	188	255	691	19.2^*1	1.0e+14	1.8e+28	288	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/05	10:48:05	259	8	392	467	519	7.6^*1	----	----	259	C2 C3 PHTX DST Java Movie	Poor Event
2017/10/05	14:12:05	289	62	261	380	849	29.7^*1	3.1e+14	1.1e+29	280	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/05	16:12:05	115	19	232	125	0	-14.7^*1	----	----	107	C2 C3 PHTX DST Java Movie	Very Poor Event
2017/10/05	20:36:05	270	53	201	122	0	-16.7^*1	2.4e+14	4.9e+28	277	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/05	22:36:07	252	44	206	470	449	8.7	2.9e+15	6.2e+29	253	C2 C3 PHTX DST Java Movie
2017/10/05	23:48:06	292	54	245	322	642	16.0^*1	1.5e+14	4.6e+28	275	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/06	08:12:05	53	10	223	131	0	-35.2^*1	----	----	59	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/06	08:48:24	269	95	320	444	397	4.9	1.2e+16	6.0e+30	264	C2 C3 PHTX DST Java Movie
2017/10/07	01:36:11	290	48	259	278	418	4.9^*1	7.4e+13	2.5e+28	287	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/07	08:24:06	281	85	338	465	494	8.3	4.7e+15	2.7e+30	279	C2 C3 PHTX DST Java Movie
2017/10/08	03:12:10	302	12	276	329	327	2.4^*1	----	----	298	C2 C3 PHTX DST Java Movie
2017/10/08	08:48:07	283	15	644	577	449	-13.5^*1	----	----	276	C2 C3 PHTX DST Java Movie
2017/10/09	04:12:05	308	15	230	222	99	-1.9^*1	----	----	301	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/09	05:36:05	271	104	327	442	416	5.3	9.6e+15	5.1e+30	264	C2 C3 PHTX DST Java Movie
2017/10/09	14:12:05	263	60	427	436	436	0.6	6.2e+14	5.7e+29	263	C2 C3 PHTX DST Java Movie
2017/10/10	03:24:05	260	16	375	470	660	15.3^*1	----	----	265	C2 C3 PHTX DST Java Movie
2017/10/10	22:36:06	298	59	450	368	173	-10.6	7.5e+14	7.6e+29	302	C2 C3 PHTX DST Java Movie
2017/10/11	06:24:05	305	51	268	319	538	9.9	3.9e+14	1.4e+29	307	C2 C3 PHTX DST Java Movie	Only C2
2017/10/11	15:12:09	285	109	741	611	585	-18.0	2.7e+15	7.5e+30	299	C2 C3 PHTX DST Java Movie
2017/10/11	20:57:24	55	15	217	251	645	15.8^*1	----	----	61	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/11	23:24:05	297	50	487	538	828	21.0	1.6e+14	1.9e+29	305	C2 C3 PHTX DST Java Movie	Only C2
2017/10/12	01:36:07	314	14	400	354	0	-13.6^*1	----	----	311	C2 C3 PHTX DST Java Movie	Only C2
2017/10/12	03:48:05	295	47	439	428	354	-3.2^*1	2.5e+13	2.4e+28	314	C2 C3 PHTX DST Java Movie	Only C2
2017/10/12	09:12:08	320	17	370	449	779	22.0^*1	----	----	313	C2 C3 PHTX DST Java Movie	Only C2
2017/10/12	19:48:05	299	22	504	677	1546	96.4^*1	6.5e+13	8.3e+28	289	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/12	23:12:12	301	18	317	199	0	-23.4^*1	----	----	309	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/13	02:48:05	316	60	315	388	851	27.9^*1	6.1e+13	3.0e+28	311	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/13	08:48:23	319	88	350	354	395	1.5^*1	2.6e+14	1.6e+29	296	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/13	21:12:10	61	13	375	325	0	-21.3^*1	----	----	68	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/14	08:48:05	307	67	413	415	434	0.8^*1	3.5e+14	3.0e+29	312	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/14	16:00:05	66	37	307	308	310	0.1^*1	3.3e+14	1.5e+29	71	C2 C3 PHTX DST Java Movie
2017/10/15	10:48:05	67	16	359	455	1059	43.2^*1	----	----	71	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/16	11:20:14	96	38	171	183	276	2.1^*1	4.2e+14	6.1e+28	101	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/16	13:46:33	86	62	213	166	0	-6.5^*1	2.7e+14	6.1e+28	102	C2 C3 PHTX DST Java Movie
2017/10/16	18:01:29	94	55	254	229	118	-2.7	8.4e+14	2.7e+29	104	C2 C3 PHTX DST Java Movie
2017/10/16	18:32:49	302	17	656	906	1731	117.2^*1	----	----	299	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/16	21:30:36	94	64	266	227	164	-2.6	8.3e+14	2.9e+29	100	C2 C3 PHTX DST Java Movie
2017/10/17	03:15:31	94	70	440	473	476	2.6	4.6e+15	4.5e+30	100	C2 C3 PHTX DST Java Movie
2017/10/17	13:22:31	86	93	362	235	0	-11.3^*1	2.7e+15	1.8e+30	110	C2 C3 PHTX DST Java Movie
2017/10/18	05:48:05	Halo	360	1576	1355	1484	-44.5	5.7e+15^*2	7.0e+31^*2	137	C2 C3 PHTX DST Java Movie
2017/10/18	08:00:05	85	146	1001	665	928	-44.3	1.1e+16^*2	5.4e+31^*2	102	C2 C3 PHTX DST Java Movie	Partial Halo
2017/10/19	14:48:06	20	91	285	376	770	23.3^*1	5.6e+14	2.3e+29	25	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/20	00:36:05	93	12	382	416	504	6.6^*1	----	----	90	C2 C3 PHTX DST Java Movie	Very Poor Event
2017/10/20	14:50:30	111	15	254	392	1163	55.6^*1	----	----	110	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/21	00:00:05	98	109	331	259	306	-2.8	8.6e+15	4.7e+30	109	C2 C3 PHTX DST Java Movie
2017/10/21	14:36:05	5	4	487	586	1347	68.0^*1	----	----	7	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/22	00:24:05	62	18	329	382	427	5.0^*1	----	----	67	C2 C3 PHTX DST Java Movie	Poor Event
2017/10/22	00:48:05	322	21	457	1050	3048	388.7^*1	1.0e+12^*2	1.1e+27^*2	321	C2 C3 PHTX DST Java Movie	Very Poor Event; Only 3 points; Only C2
2017/10/22	21:48:05	352	7	400	429	893	27.3^*1	----	----	354	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/25	03:36:05	287	11	165	145	0	-6.9^*1	----	----	284	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/26	00:12:05	76	48	161	145	0	-6.2^*1	8.7e+13	1.1e+28	77	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/26	15:12:10	248	14	148	238	623	15.8^*1	----	----	246	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/27	11:25:20	98	20	186	109	0	-41.7^*1	2.2e+13	3.8e+27	97	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/28	12:48:51	14	7	362	798	2639	289.4^*1	----	----	18	C2 C3 PHTX DST Java Movie	Very Poor Event; Only 3 points; Only C2
2017/10/28	18:00:05	296	10	412	622	1537	95.8^*1	----	----	290	C2 C3 PHTX DST Java Movie	Poor Event; Only C2
2017/10/29	17:25:20	255	24	312	345	371	2.6^*1	1.5e+15	7.4e+29	250	C2 C3 PHTX DST Java Movie	Poor Event
2017/10/29	21:25:18	267	16	159	224	269	2.9^*1	----	----	269	C2 C3 PHTX DST Java Movie	Poor Event
2017/10/30	17:00:05	256	23	296	204	0	-27.4^*1	4.6e+13	2.0e+28	258	C2 C3 PHTX DST Java Movie	Poor Event
2017/10/31	06:36:05	253	8	252	291	601	14.0^*1	----	----	254	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2
2017/10/31	11:48:05	32	8	313	314	326	0.3^*1	----	----	35	C2 C3 PHTX DST Java Movie	Very Poor Event; Only C2

*1 Acceleration is uncertain due to either poor height measurement or a small number of height-time measurements (See Section 3.4 of Yashiro et al. 2004 for details).
*2 Mass and Kinetic Energy are uncertain due to poor mass estimate. Mass measurement assumes that the CME material is in the sky-plane. Kinetic Energy is obtained from the mass and linear speed (see Vourlidas et al. 2000 for details).