From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
The Taiyo-ken (太陽拳, Taiyō-ken; FUNimation "Solar Flare"; Literally meaning "Sun Fist") is a supportive technique used by many fighters.
A good number of characters have shown the ability to use this technique during the series, but not as many as were able to use the Kamehameha. The technique is performed by the user placing their hands close to the center of their face with the fingers spread toward their eyes. The user then calls out the name and a blinding blue light fires out that blinds everything watching except the user, since they are projecting the light. Due to the fact this is simply a flash of light, it will work regardless of any gap in power between the user and the target. This technique is defensive rather than offensive, and is mainly used as way to gain the upper hand or in order to make hasty retreat. Because of the nature of the attack, it has almost always been extremely effective. The technique is rendered useless if opponent is wearing sunglasses or if they close their eyes. The technique was first used by Tenshinhan during the 22nd Tenkaichi Tournament (the Solar Flare is one of Tenshinhan's signature moves) and later on by Son Goku, Kuririn, and Cell.
Goku used it on Great Ape Vegeta in order to buy time to collect energy for the Spirit Bomb. During the fight on Planet Namek, Kuririn used it to blind Dodoria, who was chasing him after he and Son Gohan had rescued Dende. Kuririn performed his a little differently when he used it on Dodoria, however, it still produced the desired result. Kuririn later used it again against Second Form Freeza.
The only character known for a fact to be immune to the Taiyo-ken is Omega Shen Long.
The Taiyo-ken can be used to daze or stun enemies and opponents.
The Legacy of Goku
In Dragon Ball Z: The Legacy of Goku, this technique was used to temporarily stun nearby enemies.
Budokai Tenkaichi series
In the Budokai Tenkaichi video game series, it is a Blast 1 attack that causes an opponent to lose their Lock On. It is more useful in Dragon Ball Z: Budokai Tenkaichi 3 than in Dragon Ball Z: Budokai Tenkaichi 2.
In Dragon Ball Z: Shin Budokai, Kuririn can use an offensive version of the attack called "Sun Spot" which causes damage to the opponent instead of blinding them. In Dragon Ball Z: Infinite World, both Kuririn and Tenshinhan have the Solar Flare as a stun technique.
In Dragon Ball Z: Burst Limit, Tenshinhan, Kuririn, and Imperfect Cell had the Solar Flare as one of their attacks.
Attack of the Saiyans
In Dragon Ball Z: Attack of the Saiyans, there are two versions of the standard Solar Flare. Tenshinhan's version (the original version) afflicts darkness condition (which decreases a enemies accuracy). Kuririn's version allows the party to escape from battle (similar to the tactic Kuririn used to escape Dodoria). Their is also an S-Combo called Heavenly Sunlight that is a combo attack where Tenshinhan and Kuririn both unleash a Solar Flare at the same time damaging and blinding enemies. Tenshinhan also has an ultimate skill called Final Solar Flare which blinds and damages enemies (this technique is also part of the Demon-Wolf-Crane S-Combo). There are a few enemies who use the Imitation Solar Flare which works like Tenshinhan's standard Solar Flare (they are: Betrayer, Expelled Pupil, and Pupil).
- The technique's English name, Solar Flare, ties in with the Japanese name's (Taiyō-ken which means Fist of the Sun) original meaning and hints to its disruptive nature (radiation emitted by "real" Solar Flares is known to affect Earth's ionosphere and disrupt long-range radio communications) as a flash of light that blinds the opponent.
- In the North American version of Dragon Ball Z: Budokai Tenkaichi 3, Goku (GT) (when using the technique) calls the techniques by its original name, Taiyō-ken, instead of the English dub name, Solar Flare, even though he is being voiced by FUNimation voice actor Stephanie Nadolny (who voices Goku as a child). Goku (GT) is the only character (in the game's English dub) to say Taiyō-ken when using the attack, while all other characters who use it shout Solar Flare when using the technique. (Note: This only applies to the game's English dialogue.)
- This technique is useless when the oponent or people near him uses sunglasses. This is evident in the 22nd Tenkaichi Tournament when Tenshinhan uses the technique against Roshi affecting him, while Master Shen and the tournament commentator seem unaffected by the flash. In the finals of the same tournament, Goku borrows Roshi's sunglasses to prevent Tenshinhan's Solar Flare and he is even capable of hitting Tenshinhan during the execution of the technique. This is also proven in the 23rd Tenkaichi Tournament when Goku uses the technique during his fight with Tenshinhan which effects everyone but Roshi and the announcer.
- Omega Shenron is the only character to show immunity to the Solar Flare.
- In the original manga, each person who uses Solar flare uses it only twice. In the 22nd Tenkaichi Tournament, Tenshinhan uses it once against Muten Roshi (as Jackie Chun) in the semifinals, and then on Goku in the finals. In the next tournament, Goku uses it on Tenshinhan in the semi-finals and then on Great Ape Vegeta in the Saiyan Saga while collecting energy for the spirit bomb. Kuririn uses it on Dodoria on Planet Namek to escape with Gohan and Dende, and on Frieza's second form. Finally, Cell uses it on Piccolo, Future Trunks, and Kuririn. In his next form, he uses it on Trunks again, but it also affected Kuririn, Artificial Human No. 16, and Artificial Human No. 18.